I am trying to crawl a site using mechanize. The site provides search results in different pages. When posting to get the next set of results, something is wrong and the server redirects me to the first page, asking mechanize to update the SearchSession Cookie.

I have been debugging the requests using Firefox and they look quite the same, and I am unable to find the problem. Any suggestion? Below the requests:

----------- FIRST THE RIGHT SEQUENCE, USING TAMPER IN FIREFOX ------------------------- POST XXX/JobSearch/Results.aspx?Keywords=Python&LTxt=London%2c+South+East&Radius=0&LIds2=ZV&clid=1621&cltypeid=2&clName=London Load Flags[LOAD_DOCUMENT_URI LOAD_INITIAL_DOCUMENT_URI ] Content Size[-1] Mime Type[text/html] Request Headers: Host[www.cwjobs.co.uk] User-Agent[Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100401 Ubuntu/9.10 (karmic) Firefox/3.5.9] Accept[text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8] Accept-Language[en-us,en;q=0.5] Accept-Encoding[gzip,deflate] Accept-Charset[ISO-8859-1,utf-8;q=0.7,*;q=0.7] Keep-Alive[300] Connection[keep-alive] Referer[XXX/JobSearch/Results.aspx?Keywords=Python&LTxt=London%2c+South+East&Radius=0&LIds2=ZV&clid=1621&cltypeid=2&clName=London] Cookie[ecos=774803468-0; AnonymousUser=MemberId=acc079dd-66b6-4081-9b07-60d6955ee8bf&IsAnonymous=True; PJBIPPOPUP=; WT_FPC=id=86.181.183.106-2262469600.30073025:lv=1272812851736:ss=1272812789362; SearchSession=SessionGuid=71de63de-3bd0-4787-895d-b6b9e7c93801&LogSource=NAT] Post Data: __EVENTTARGET[srpPager%24btnForward] __EVENTARGUMENT[] hdnSearchResults[BV%2CA%2CC0P5x%2COou-%2CB4S-%2CBuC-%2CDzx-%2CHwn-%2CKPP-%2CIVA-%2CC9D-%2CH6X-%2CH7x-%2CJ0x-%2CCvX-%2CCra-%2COHa-%2CHhP-%2CCoj-%2CBlM-%2CE9W-%2CIm8-%2CBqG-%2CPFy-%2CN%2Fm-%2Ceaa%2CCvj-%2CCtJ-%2CCr7-%2CBpu-%2Cmh%2CMb6-%2CJ%2Fk-%2CHY8-%2COJ7-%2CNtF-%2CEya-%2CErT-%2CEo4-%2CEKU-%2CDnL-%2CC5M-%2CCyB-%2CBsD-%2CBrc-%2CBpU-%2Col%2C30%2CC1%2Cd4N%2COo8-%2COi0-%2CLz%2F-%2CLxP-%2CFyp-%2CFVR-%2CEHL-%2CPrP-%2CLmE-%2CK3H-%2CKXJ-%2CFyn%2CIcq-%2CIco-%2CIK4-%2CIIg-%2CH2k-%2CH0N-%2CHwp-%2CHvF-%2CFij-%2CFhl-%2CCwj-%2CCb5-%2CCQj-%2CCQh-%2CB%2B2-%2CBc6-%2ChFo%2CNLq-%2CNI%2F-%2CFzM-%2Cdu-%2CHg2-%2CBug-%2CBse-%2CB9Q-] __VIEWSTATE[%2FwEPDwUKLTkyMzI2ODA4Ng9kFgYCBA8WBB4EaHJlZgWJAWh0dHA6Ly93d3cuY3dqb2JzLmNvLnVrL0pvYlNlYXJjaC9SU1MuYXNweD9LZXl3b3Jkcz1QeXRob24mTFR4dD1Mb25kb24lMmMrU291dGgrRWFzdCZSYWRpdXM9MCZMSWRzMj1aViZjbGlkPTE2MjEmY2x0eXBlaWQ9MiZjbE5hbWU9TG9uZG9uHgV0aXRsZQUkTGF0ZXN0IFB5dGhvbiBqb2JzIGZyb20gQ1dKb2JzLmNvLnVrZAIGDxYCHgRUZXh0BV48bGluayByZWw9ImNhbm9uaWNhbCIgaHJlZj0iaHR0cDovL3d3dy5jd2pvYnMuY28udWsvSm9iU2Vla2luZy9QeXRob25fTG9uZG9uX2wxNjIxX3QyLmh0bWwiIC8%2BZAIIEGRkFg4CBw8WAh8CBV9Zb3VyIHNlYXJjaCBvbiA8Yj5LZXl3b3JkczogUHl0aG9uOyBMb2NhdGlvbjogTG9uZG9uLCBTb3V0aCBFYXN0OyA8L2I%2BIHJldHVybmVkIDxiPjg1PC9iPiBqb2JzLmQCCQ8WAh4HVmlzaWJsZWhkAgsPFgIfAgUoVGhlIG1vc3QgcmVsZXZhbnQgam9icyBhcmUgbGlzdGVkIGZpcnN0LmQCEw8PFgIeC05hdmlnYXRlVXJsBQF%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%3D] Refinesearch%24txtKeywords[Python] Refinesearch%24txtLocation[London%2C+South+East] Refinesearch%24ddlRadius[0] ddlCompanyType[0] ddlSort[1] Response Headers: Cache-Control[private] Date[Sun, 02 May 2010 16:09:27 GMT] Content-Type[text/html; charset=utf-8] Expires[Sat, 02 May 2009 16:09:27 GMT] Server[Microsoft-IIS/6.0] X-SiteConHost[P310] X-Powered-By[ASP.NET] X-AspNet-Version[2.0.50727] Set-Cookie[SearchSession=SessionGuid=71de63de-3bd0-4787-895d-b6b9e7c93801&LogSource=NAT; path=/] Content-Encoding[gzip] Vary[Accept-Encoding] Transfer-Encoding[chunked]

-------- NOW WHAT I'AM SENDING USING MECHANIZE, SOME HEADERS ADDED, ETC ----------- POST /JobSearch/Results.aspx?Keywords=Python&LTxt=London%2c+South+East&Radius=0&LIds2=ZV&clid=1621&cltypeid=2&clName=London HTTP/1.1\r\nContent-Length: 2424\r\n Accept-Language: en-us,en;q=0.5\r\n Accept-Encoding: gzip\r\n Host: www.cwjobs.co.uk\r\n Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8\r\n Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n Connection: keep-alive\r\n Cookie: AnonymousUser=MemberId=8fa5ddd7-17ed-425e-b189-82693bfbaa0c&IsAnonymous=True; SearchSession=SessionGuid=33e4e439-c2d6-423f-900f-574099310d5a&LogSource=NAT\r\n Referer: XXX/JobSearch/Results.aspx?Keywords=Python&LTxt=London%2c+South+East&Radius=0&LIds2=ZV&clid=1621&cltypeid=2&clName=London\r\n Content-Type: application/x-www-form-urlencoded\r\n\r\n' '__EVENTTARGET=srpPager%24btnForward& __EVENTARGUMENT=& hdnSearchResults=BV%2CA%2CC0eif%2CMwc%2CM6s%2COou%2CK09%2CG4H%2CEZf%2CGTu%2CLrr%2CGuX%2CGs9%2CEz9%2CL5X%2CL9U%2ChU%2CHHf%2CMAL%2CNDi%2CJrY%2CGBy%2CM%2Bo%2CdE-%2CpI%2CtDI%2CL5L%2CL7l%2CL8z%2CM%2FA%2CPPP%2CCM0%2CEpK%2CHPy%2Cez%2C7p%2CJ2U%2CJ9b%2CJ%2F2%2CKea%2CLBj%2CLvi%2CL2t%2CM8r%2CM9S%2CM%2Fa%2CPRT%2CPgi%2Csg7%2CF6%2CI2F%2CJTd%2CO-%2CC0v%2CC3f%2CDCq%2CDxn%2CERl%2CUbV%2CGME%2CGMG%2CGd2%2CGgO%2CGyK%2CG0h%2CG4F%2CG5p%2CJGL%2CJHJ%2CKhj%2CL4L%2CMM1%2CMYL%2CMYN%2CMp4%2CNL0%2COrj%2CvuW%2CBdE%2CBfv%2CI1i%2CBCh-%2COLA%2CHH4%2CM6O%2CM8Q%2CMre& __VIEWSTATE=%2FwEPDwUKLTkyMzI2ODA4Ng9kFgYCBA8WBB4EaHJlZgWJAWh0dHA6Ly93d3cuY3dqb2JzLmNvLnVrL0pvYlNlYXJjaC9SU1MuYXNweD9LZXl3b3Jkcz1QeXRob24mTFR4dD1Mb25kb24lMmMrU291dGgrRWFzdCZSYWRpdXM9MCZMSWRzMj1aViZjbGlkPTE2MjEmY2x0eXBlaWQ9MiZjbE5hbWU9TG9uZG9uHgV0aXRsZQUkTGF0ZXN0IFB5dGhvbiBqb2JzIGZyb20gQ1dKb2JzLmNvLnVrZAIGDxYCHgRUZXh0BV48bGluayByZWw9ImNhbm9uaWNhbCIgaHJlZj0iaHR0cDovL3d3dy5jd2pvYnMuY28udWsvSm9iU2Vla2luZy9QeXRob25fTG9uZG9uX2wxNjIxX3QyLmh0bWwiIC8%2BZAIIEGRkFg4CBw8WAh8CBV9Zb3VyIHNlYXJjaCBvbiA8Yj5LZXl3b3JkczogUHl0aG9uOyBMb2NhdGlvbjogTG9uZG9uLCBTb3V0aCBFYXN0OyA8L2I%2BIHJldHVybmVkIDxiPjg1PC9iPiBqb2JzLmQCCQ8WAh4HVmlzaWJsZWhkAgsPFgIfAgUoVGhlIG1vc3QgcmVsZXZhbnQgam9icyBhcmUgbGlzdGVkIGZpcnN0LmQCEw8PFgIeC05hdmlnYXRlVXJsBQF%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%3D& Refinesearch%24txtKeywords=Python& Refinesearch%24txtLocation=London%2CSouth+East& Refinesearch%24ddlRadius=0& Refinesearch%24btnSearch=Search& ddlCompanyType=0& ddlSort=1'