I've been unable to reproduce it either. However It has dawned on me that it might have coincided with a change of username on geocaching.com. That could explain that it found the account but couldn't find the filters?
This is conjecture at this stage, what I'd noticed was that the green filter active icon wasn't active. Turning it back on fixed the issue. At the time it was still showing my old username in the top right panel, yet the username and changed on geocaching.com. Thus I suspect this might be the root problem.
In any case the filter routine was hanging indefinitely waiting for completion which suggests a missing timeout value for the routine which would help users on slow connections anyway. Very low priority fix I would suggest.