Just tested. Removed tick from Show balance data and the worker stats appeared. If this is helping.
Sussed it, thanks. The "Show worker data" box had somehow become unticked (why? who knows?)
If this happens, then after the next data refresh and until the program is restarted, the workers are still displayed, but the hash rate changes to ZERO.
On closing and restarting, the worker page is then blank, and the hash rate is ZERO.
If the box is then ticked, the workers and hash rate are displayed after the next data refresh, even without a restart.
Perhaps this needs a tweak, as I'm sure the hash rate should continue to be displayed even if the actual workers are not, and the behaviour when the box is ticked/unticked is inconsistent.
I'm not seeing the error which testicus has posted, though.
I think is working correctly. The output from ScryptGuild doesn't have a total hash rate for the user, it only has it per worker. The program has to add it up to show the total. Therefore if you turn off the worker data, there is nothing to total up and your total becomes zero.
I don't think I disable that checkbox anywhere in the code, so you must have unclicked it by accident.