There is a topic by essentially the same name, but my answer leads to another question which I would like answered so... My case is as follows:

I connect through SSH to my server... no problems for many months on Ubuntu Server 9.04. Eventually I decided to updgrade and straight away I get the 10 minutes freeze problem. I went through all the possible fixes (many can be found here but my quick fix, the only that worked, leaves me with no real answer as to why and how to properly correct it...

As ridiculous as it sounds... while I leave a keyboard plugged in... it runs without flaw.

Can anyone make sense of this?

For the sake of completeness, (although none of the following made any difference upon subsequent completion), some of the permanent changes I have made while trying to correct the issue are: replacing samba config file with 9.04 backup, booting with noapic and modifying sysctl.conf, just uncommenting additional settings for enhanced security.