First I had added a new product to Bugdar. Then I added a new Status and made a spezial Usergroup. After that, I created a bug. Then, I opened this bug an set it to "hidden". Then I could no longer open this bug and I received an error-message (I think it was something with line 40 ...).
From this time, I always saw this bug and could not open it. So I decided to delete the Status, the Usergroup and the Product. The bug was away, but now I unfortunately cannot search any more.
Clicking the search, this message comes:
Error: No search results were returned that mached your criteria. Even if I click again, it comes always the same message.
What can I do? I like your program very much!

Additional comment: now I have deleted some of my saved searches, and now it seems that I can search again. However, there must be a bug which has to do with the setting of the hidden field.

I cannot reproduce this. Can you check and see if setting a bug as "Hidden" causes any problems? What version of Bugdar are you testing with?

I am testing with 1.2.0 Release Candidate 1. Using now the hidden field again, I am worry that the search may not work again ... I will try it later (after our actual project).

You could setup a test installation separate from your main one and you could try reproducing it there. I just followed again the steps you outlined in your initial report and I could not replicate it.