Windows startup failed because of error with Avast! Antivirus

Hi guys,
An error message appears every time I try to start up Windows. This message was a little bit different before. It has changed after I removed the rpcqt.dll file with the help of Avast! 6 Free Antivirus. The message I found before was this:
"The file could not be run because it contains a virus."
Note that message was also from RunDLL, not Avast! The new message is this:
"There was a problem starting C:UsersMatthewAppDataLocalTempRpcqt.dll. The specified module could not be found."
Does anyone have any idea about this file? Why do I receive an error every time I start my PC, and how can I get rid of this situation?
Thanks in advance.
