Look in your startup-sequence, if there is anything started that is running in the background. Remove everything that is non-essential and try to reproduce the problem.
It *might* as well be some hardware issue. As I wrote above, the gurus are in almost all cases consequences of other problems, like programming errors (overwriting memory, bad pointers, etc etc), bad memory, you name it. They are really only helpful to the programmer.
Is the other number (#81...5.XXXXXXXX, I mean the XXXX here) always the same?