Adobe Acrobat X Pro refuses to open
Earlier, I tried to open one of my PDFs with Acrobat 10... nothing. Thinking I hadn't actually clicked the PDF correctly, I tried again. Then a few more times (the software variant of "percussive maintenance"). Finally I tried simply opening Acrobat itself, thinking there was something wrong with the file associations. Nothing. I open up task manager to find that when I try to launch Acrobat, acrobat.exe pops up for a brief moment, and then disappears. There are no error dialogs or anything, the application simply closes immediately.
So, I try opening the PDF in Firefox using file://drive:/path/. Nothing, again. No problem opening the containing folder (on an external hard drive), but clicking the link to the file results in nothing happening. Open with Adobe Reader X? It works perfectly, of course!
This is a recent install of Acrobat X Professional (exactly 1 week, today) on Windows 7 Home Premium. This is a fresh install, not an upgrade. The PDF is over 2 years old (not that other PDFs work, mind you). Acrobat worked when I tested it after installing, so something has changed, I just don't know what.
Any help would be appreciated! :)