Goldendict, which is also a QT-based program, goes crazy up into 100% CPU usage when doing full-text searches.
Nevertheless, i haven't yet seen a BSOD caused by that... which IMO points to something wrong hardware-wise in your system as Leseratte said in the first reply, or maybe driver related.
I often see Kovid suggesting
this workaround for some e-book Viewer issues, but I'm not sure if that could help in this case.