Where did you get the After Effects CS5 trial version? Only the After Effects CS5.5 trial version is available.
You mentioned trying a few things already, but there are some possible solutions here that you haven't mentioned trying:
Yeah CS5.5 from the adobe website. At least I think so - my internet connection is to slow to download anything, so a friend got it for me
The point: permissions problem with preferences folder or corrupt preferences - I don't know why, but I don't have the AppData\Roaming path/folders
just worked through this discussion: blockage of TCP communication with QuickTIme - I don't quite get the point with the rule ... what steps do I have to follow in Windows Firewall? but well I deactivated it anyway and it still didn't work.
Aaand I don't find the preference files on windows ... user/...
gosh I want to work with this program error-free ^^
but I don't have the AppData\Roaming path/folders
You have it, it's just invisible by default. Check your folder view options and turn off the hide system folders checkbox. The rest - well, you have some serious permissions, group policies or network issues, despite what steps you already have taken. nothing else explains such severe slowdowns and al lthe problems you are facing. That being so, you are either having a virus or you are not telling us something...