ErrorContextCallback

Hi!

Sorry if I post this mail to the wrong list, I checked each by it's
theme and this seems to be the best.
I have a strange problem with an errorcontextcallback:
Given the following code fragment:
mycallback->previous = error_context_stack;
elog(DEBUG1,"1");
mycallback->callback = plpgj_ErrorContextCallback;
elog(DEBUG1,"2");
mycallback->arg = "hello world!";
elog(DEBUG1,"3");
error_context_stack = mycallback;
elog(DEBUG1,"4");

and the callback function logs "callback", the following apears in the log:
DEBUG: 1
DEBUG: 2
DEBUG: 3
ERROR: callback

Can anybody tell me why this happens?

Thanks,
Laszlo