Creating new text and rating custom columns in broken in 0.7.3. If you create one, the tag browser stops working. Deleting the column restores the tag browser's functionality.
Kovid will decide when the fix will be released, but I imagine that it will be sooner rather than later.
This problem does *not* affect use of custom columns you created in previous releases. It does not affect comment, boolean, integer, date, and float columns.
Apologies to all for my failure to adequately test and find this problem before release.