i don't know if this is of any consequence:
(xp only) many people have had problems with the install of net 3.5, because their registry was improperly (manually) altered from the previous net framework edition. i personally had to uninstall all net framework packages back to 1.1, and then reinstall all of them starting with the 2.0 package and then the 3.5 and so on...blah blah..
note: i had never manually altered the registry, but i used a tool to remove some "left over" install data. this is where my problem came from. also, the 3.5 package (before i uninstalled anything)initially installed properly (or so it looked) but it didn't install the full package.
going back to 1.1 , then reinstalling all remaining net framework has solved many problems related to the 3.5 install.
believe me...there are a lot of problems related to that install!
-the dude