Here are the steps I use to just scan a single folder for dups when the problem occurs:
Start Image Comparer
Set similarity range from 95 to 100%
Click on Compare folders button
Add folder to scan
Set database limit to 99
Click on Compare button
Similarity range automatically changes to 100 to 100 percent. (the problem)
Creating database dialog window appears.
Quite a simple procedure. Not sure what I'm doing wrong.