Filter Forge 4 has stopped working

Three days ago I tried to open my FF 4 version as a stand alone and it froze my computer. For the last three days I have updated everything I can think of and have cleaned everything on my computer. I have opened every other program on my computer and have had no problems with them opening or crashing. Nothing is broken except my FF4. I also have FF 3 installed and it works perfectly. But every time I open (or try to open) FF4 my computer freezes, the program never starts and I have to restart my computer. I uninstalled FF4 three times and downloaded from the website and reinstalled, nothing worked. It still wouldn't open. I went through some old download files on my computer and found an earlier download. It worked and I got it installed, but of course it wanted me to update to the newer version which I did. It downloaded and reinstalled and again it froze my computer. So I have no idea what could be wrong or what is hanging it up. Any help would be greatly appreciated. It was working without a hitch until three days ago. I use it almost daily.

I have Windows 7 home edition

Thanks grosvenor, I did that too. I went back a month and it still didn't help. It could be malware but it is weird that it is only FF4 that it is effecting. My computer or other programs haven't slowed or crashed. The only things I have downloaded in the last month has been filters from this site. I haven't downloaded a new program in ages either. I'm still checking things, but so far I can't get anything to help.

Glad to know the issue has been fixed.
If someone is reading this in the future: one of the fist things to do when Filter Forge misbehaves several times in a row, even after a reboot, is to rename or remove the %APPDATA%\Filter Forge 4\ folder on Windows or /Users/Your_User_Name/Library/Application Support/Filter Forge 4/ on Mac.