OS X :: IMovie Won't Import Anything?

So, I've seen tons of threads about iMovie only working with certain video file extensions and not others. Trouble is, my iMovie doesn't work with any file, ever. The files show up as "importable" when I go to import them, but then they simply don't import. When I try clicking and dragging them like the program says to, they "bounce back" to where they were. When I click on "last import" it shows up empty.When I click on "import" it acts as if it's going to work, and an icon reading "new event" shows up, but when I highlight (or click, or double click, or right-click, or anything) that icon, the message reads, "No matching video. Chose a different option from the Show pop-up menu" etc.

I've been trying for months! I love to make videos and with Vegas on Windows I never had any trouble. Files that iMovie won't import: AVI, MP4, MP3, MPG, MKV, WMV, SFK, and no song files, either.My Mac is an iMac OS X version 10.5.8I called the local Apple store and the lady there told me that I shouldn't be trying to use any videos other than ones I'd shot from my own camera anyway. :/