Naughty SP Ruining My Day!?!

Hi!

Running a SQL2K-server on a Win2K(adv) I have sort of an enigma (to me atleast!):

One of my SPs sometimes seems to hang. Arrgh. This is of course not the total extent of my problem - naah, I've had/created my share of faulty SPs which hang on a regular basis - no, the enigma is that the code inside my SP *never* hangs when executed from the Analyser? The test is done using ctrl-a/copy&paste - remove 'Create...' and putting a 'Declare in front of the only parm, then inserting a select parm='value_of_parm'. As far as my knowledge goes this 'running code from SP in Query Analyser' should introduce no extra room for slack (which in turn could help me explain why the code works in Query Analyser)?

Btw, when I say 'hang' it's not the whole truth - using the debugger I can see the code (mostly a bunch of updates on one table) being executed - but extremely slow. The code takes approx. 1 min in Query Analyser but hasn't finished after 60 mins when executing the SP.

A little info on the SP:
The user runs another SP which gathers some data from an Oracle DB and inserts these data into a SQL2000 table. Then the user activates the above flamed SP in vain hope of marking the newly fetched data with a statusid.
The problem allways arises when the user tries to let the SP engage newly fetched data - and rarely when engaging old (already marked, hence 'remarking') data. I suspect this could be a clue for anyone with some insight?

I'm looking for 1) a solution, 2) a finger pointing out the bug(s) 3) any suggestions on how to do further research into this evil SP!

Thanx in advance!
Ult