Recovering from backtrace problem

I'm not sure about this, but i'm having strange things. Here is a description. I have non-nil value for `debug-on-error'. I'm working in XEmacs as usual, editing files, running compilator, etc etc. At one moment error occurs and *Backtrace* buffer pops up, but i need some task todo atm so i switches from backtrace(keeping it for further investigation) to some other buffer, continuing to work. Than i totally forgot that i have *Bactrace*, passed ~30-90 minutes since an error occured and *Backtrace* buffer poped up. Then i saw square brackets in the modeline and decided to examine backtrace. When i was done with it i pressed `q'. From this point, strange things starts, frame's minibuffer totally broken, can't even enter a character to it. XEmacs stops responding to key/mouse presses in this frame(however it continues responding in other frames). I closed this frame and create another - from this point everything continued working ok. I noticed if i examine backtraces when they just pops up and press `q' at the end - such behaviour not triggered. What can cause such behaviour? Actually i can live with it, but sometimes it annoys much. Thanks for advices! -- lg