I'm having a hard time fixing this. It seems to be a bug in jQuery UI's buttonset() function (maybe related to this SO answer:
http://stackoverflow.com/a/18219375). I managed to fix the problem in the Name/Date filter by explicitly destroying the button set before doing the AJAX request. But for some reason I absolutely don't understand this breaks the Row/Thumb filter after the name/date AJAX request.
Something isn't right here in how the buttonsets are managed (the error occurs inside jQueryUI) but I can't figured out where it goes wrong.
I pushed my changes to a separate branch:
https://github.com/splitbrain/dokuwiki/compare/fs2851
Current state: on fresh page load, row/thumb works fine on it's own, date/name work fine on it's own. But once date/name was used row/thumb will break. You can navigate the namespace tree and the behaviour will be exactly as if a fresh page load occured (even though it is only an AJAX refresh). Sorting on search results doesn't work currently but that's a different problem that can be solved relativly easy once we figured out this bug.