What language?

"all comparing statements do lead to a definite address"

But are all conditions fully handled; eg, do all your switch statements have a default?

Are all your pointers correctly initialised?
There was a "weird problem" on the Keil site recently which turned out to be due to an uninitialised pointer.

Are you sure that all index values are valid before accessing arrays, lookup tables, jump tables, etc?

Could you be getting a buffer overrun - this could be particularly drastic if your buffer overruns onto the stack, or maybe corrupts some pointers...