In the latest release of Alpha Application Server 5887_5315 BitDefender thinks the file: A5SQLDBSQLServer.dll is malware, and moves it to the quarantine when it can get access to it.

You'll find that your website will begin to slow down, until BitDefender can 'grab' the file, and then you won't be able to access the site, or login if you have a SQL database.

Add this file (or the alpha directory) to the exclusions..