For the most part, I am very impressed with Anime Studio... except for one thing

I have been working on a character and saved him to a file. I checked the file before and had no problems with it. Now, when I try to open it, an exclamation mark pops up saying:
Can Not Open File
Error Details:
...And that's it. It contains no error details. All of my other files work perfectly fine and haven't downloaded any viruses.
Can anybody help? I need it for an animation which is due in 20 days!