Hi, I'm developing an asp.net application that has to run on an IIS 5.1
virtual server under XP professional, which works perfectly all right on my
machine (where it's developed). The trouble is that it doesn't work on the
machine where it's supposed to. And it's only when an insert or an update has
to be done, querying the database is no problem. I don't get any errors but
the buttons just fail, period. They don't even perform a lousy postback.

I've tried updating windows and the .net service pack 1.1 (the target
computer is off-line most of the time) but that was no help. I'm running out
of options here, so help... please

I don’t know how helpful this may be.
I have had similar problems like this earlier. Sometimes the IDE takes off the handles keyword which binds the events to objects when u move the code around. Double check for that.
If the handles keyword is not there the server execution will not trigger.