Hmm, the "pydbgp" reference is a UI mistake from sharing some of the setup UI, it's using the right protocol underneath.
Nothing looks obviously wrong with the dbg.xml. With a timeout like that, it sounds like something that could have prevented the debuggee from connecting back to our debugger. If the debuggee had died, we would pick up on that before a full timeout.
We can enable some debug logging. Restart SlickEdit, go to the SlickEdit command line and type in "set-var def-debug-logging 2", and then try to attach the debugger. This will produce some output in the Build window. (and if it gets far enough, also some output will go into your configuration directory under logs/debug.log. On windows, the default configuration directory is under Documents\My SlickEdit Config. You can also see it in the Help -> About dialog).
Post the output from those two places. And afterwards, run "set-var def-debug-logging 0", it's a persistent setting and can build up a large set of logs pretty fast.
It probably doesn't matter, but what version of SBT are you using?