Hey, I had a similar problem as jimarick in which DIF4U would start the DVDDecrypter sessions before the previous one had finished. A ton of DVDDecrypter sessions would be loaded and crash the system. Well, the cause of that problem for me was a trojan. regsrv.exe had been running in the task manager and trying to access the internet and is a part of Backdoor.OptixPro. Backdoor.OptixPro also copies winampw.exe in a system folder and changes a registry setting to load it whenever an .exe is run. I hypothesize that since winampw.exe was being run and then the .exe you want to run is called, DIF4U cannot properly detect that DVDDecrypter is finished, or it receives the finished command immediately, and runs all the DVDDecrypter sessions before the previous had finished. The solution to my problem was to remove the trojan. Here are some links that explain how to remove it: I also removed and reinstalled my firewall and antivirus software because Optix attacks them. This trojan is commonly spread by an infected trillian download from kazaa. Hope I was of help to those with problems. Thanks to Eyes`Only for recognizing regsrv.exe as a virus. Mechannibal