Sometimes after some bad spyware gets on the computer, even after it is 'removed' it does not get fixed. You need to run a program called 'hijack this.' This is a long and tedious process, where it generats a log, there are a number of sites including
this (which is ok, i am nto at work so do not have the forum link i normally post to here). Basically they will tell you what has to be removed from the log file, and that should repair it.
That is sadly the bad part of some of the spyware, it messes stuff up so bad, that it is almost just better to re-install.