Blind shot: right click the WC root and select TSVN -> Cleanup ....
Make sure Fix time stamps is selected and click OK. Note I'm really not sure whether this helps or not, but in the past I ran into situations where exactly this was causing a significant slowdown as you described.
Alternatively try a fresh checkout (removing the old one) and see if this solves the performance issue you are experiencing.
Temp workaround could also to (temporarily) disable the status
cache for the problematic working copy (TSVN settings -> Icon
Overlays -> adjust the settings (especially Exclude paths) to
narrow down whether it's an issue with a particular repository and
the status cache - see the docs for descriptions on the other
settings in that dialog which might help to find a workaround
and/or narrow down the issue as well).
-- Regards, Stefan Hett, Developer/Administrator
Thanks for that, I started the Cleanup and it's taking just as long as checking for a commit! I'll let you know how it goes and if the other steps you suggested have an impact.
A fresh checkout would be a significant undertaking, it's a 55GB repository with between 20k and 30k files and I'll be pulling it down over ADSL until broadband is installed in my area between now and September... so hopefully that's not required!