Have you updated your Java lately? current version is 6.1
When you sign in here do you check box which says "remember me"? If you do that you should have to keep signing in.
Use ONLY Firefox and set it as your DEFAULT browser and see if you keep having these problems. Firefox has the option of always remembering user name and password for various websites if you wish to use it.
Let me know if any of this makes a difference.
To control Start Ups use Mike Lin's StartUp Control Panel. It is FREE, small and very easy to use.
ALL of these items can be removed from Auto Start with Mike Lin's
ibmmessages
StorageGuard
Microsoft Works Update Detection
TempRemove
TkBellExe
iTunesHelper
QuickTime Task
MSMSGS
RealPlayer
PlaxoUpdate
Acrobat Assistant
Microsoft Office
WinZip Quick Pick