I am on Ubuntu 11.10/64bit with Gnome 3.

Regards

[update] I trying to say that when I start an application like Nautilus LibreOffice starts as well. Sometimes this also happens when I open a document with a totally different extension i.e. a .html doc. I checked if and which plugins are installed to Firefox:

OpenOffice.org Plug-in

File: libnpsoplugin.so
Version: 
OpenOffice.org Plug-in handles all its documents

MIME Type   Description     Suffixes


application/vnd.stardivision.calc   StarCalc 3.0 - 5.0  sdc
application/vnd.stardivision.chart  StarChart 3.0 - 5.0     sds
application/vnd.stardivision.draw   StarDraw 3.0 - 5.0  sda
application/vnd.stardivision.impress    StarImpress 3.0 - 5.0   sdd
application/vnd.stardivision.impress-packed     StarImpress-packed 3.0 - 5.0    sdp
application/vnd.stardivision.math   StarMath 3.0 - 5.0  smf
application/vnd.stardivision.writer     StarWriter Template 3.0 - 5.0   vor
application/vnd.stardivision.writer-global  StarWriter Global 3.0 - 5.0     sgl
application/vnd.staroffice.writer   StarWriter 3.0 - 5.0    sdw
application/vnd.sun.xml.calc    StarOffice 6.0/7 Spreadsheet    sxc
application/vnd.sun.xml.calc.template   StarOffice 6.0/7 Spreadsheet Template   stc
application/vnd.sun.xml.draw    StarOffice 6.0/7 Drawing    sxd
application/vnd.sun.xml.draw.template   StarOffice 6.0/7 Drawing Template   std
application/vnd.sun.xml.impress     StarOffice 6.0/7 Presentation   sxi
application/vnd.sun.xml.impress.template    StarOffice 6.0/7 Presentation Template  sti
application/vnd.sun.xml.math    StarOffice 6.0/7 Formula    sxm
application/vnd.sun.xml.writer  StarOffice 6.0/7 Text Document  sxw
application/vnd.sun.xml.writer.global   StarOffice 6.0/7 Master Document    sxg
application/vnd.sun.xml.writer.template     StarOffice 6.0/7 Text Document Template     stw
application/vnd.oasis.opendocument.text     OpenDocument Text   odt
application/vnd.oasis.opendocument.text-template    OpenDocument Text Template  ott
application/vnd.oasis.opendocument.text-master  OpenDocument Master Document    odm
application/vnd.oasis.opendocument.text-web     HTML Document Template  oth
application/vnd.oasis.opendocument.spreadsheet  OpenDocument Spreadsheet    ods
application/vnd.oasis.opendocument.spreadsheet-template     OpenDocument Spreadsheet Template   ots
application/vnd.oasis.opendocument.graphics     OpenDocument Drawing    odg
application/vnd.oasis.opendocument.graphics-template    OpenDocument Drawing Template   otg
application/vnd.oasis.opendocument.presentation     OpenDocument Presentation   odp
application/vnd.oasis.opendocument.presentation-template    OpenDocument Presentation Template  otp
application/vnd.oasis.opendocument.formula  OpenDocument Formula    odf