You could try this:
Download a complete backup from your webhotel to your pc, then download and install this program- TotalCommander from here: http://www.ghisler.com/
Then use the Totalcommander option- “Find Text (Commands/Search/Find Text”, put in the address for the spam site and let it search through your backup.
This might tell you, where to find the solution.
/ptj_11
Could You tell me, what address the spamsite has?
/ptj_11
Try cleanig our browser cache, and then try again.
/ptj_11