i'd actually managed to find that out with a bit of digging and realised i already had something running on that port. bit of tweaking managed to get that sorted out and jsonrpc is now running happily, by all accounts.
the next question, of course, is whether anything actually works
so far, i've verified that i can shut it down from the web interface (using, i assume the event server) so that's looking good. i need to trigger a library update next, but i'll be configuring all of my sources to match the other xmbc instances on my network first. not too bothered about trashing that - in the absolute worst case, it can be rebuilt from the metadata stored with the media files themselves. i've plugged mediafrontpage in front of it, and that seems to be able to see and stop the server, too, although i've not had a chance to test the library side of it yet.
anyone else used the patchfile to get it working for yourself yet? or has anyone found anything more out about the broken mysql connections side of things?