Your user agent string which identifies the version of Firefox you are using is this: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.14) Gecko/2009082707 Firefox/3.0.14 (.NET CLR 3.5.30729)

That is a user agent for Firefox 3.0.14, are you sure you do not have 3.0.14? Some add-ons will change parts of the user agent string. Typically they change the part containing the Firefox version number, they do not normally change the parts such as the Gecko date or build number, both of which for your user agent string are those of Firefox 3.0.14

The Firefox 3.6.8 user agent string is like this one: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8

All the indications are that you have Firefox 3.0.14, but if you are certain that you have Firefox 3.6.8, you can reset the user agent string. For details see websites or add-ons incorrectly report incompatible browser. An

You can see the Firefox version at the top and the user agent at bottom of the "Help > About" window (Mac: Firefox > About Mozilla Firefox).
You check (compare) what websites see: http://whatsmyuseragent.com/ - Whats My User Agent?

If you have Firefox 3.6.x then you need to check the general.useragent prefs on the about:config page.
You can open the about:config page via the location bar, just like you open a website.
Filter: general.useragent
If general.useragent prefs are bold (user set) then you can right-click that pref and choose Reset.

In your case it should be the pref general.useragent.override that is set to a Firefox 3.0.14 user agent