Since I downloaded the game, I've had that bug: when I used either shootdown or multishot, my game was crashing saying that there was no disk in drive. Today, I found the solution.
1. First, you have to right clic on the patcher.
2. Clic on solve compatibility problem.
3. follow the step, saying your problem is not their list.
THEN COMES THE QUESTION. Was this application working on previous windows version (Something like that)
Press YES, and select windows 7
4. Execute the patcher as admin.
5. Save the changes.
6. Enjoy
If this works for other players, feel free to create another thread with a detailed version. I was getting tilted at this bug.