SaleMaker won't load up

ZC Version 1.5.1

I'm trying to setup an end of year sale on all cross stitch charts. I click on SaleMaker and then New Sale and it spins and spins and spins and never loads up the checkboxes. I've deleted all my old sales which didn't help.

The admin end of my site has always been a tiny bit slow, but nothing I couldn't live with, but this won't work at all. What else can I try to get this working?

My site is http://laurelsstitchery.com/catalog/. Any help would be greatly appreciated! :)

Could you look, via phpMyAdmin, and see how many records are in the table:
categories

When is the last time you were able to Add/Edit a Sale?

Have you made any changes since?

If you peek in the Tools ... Server Info ... what do you see on the Server Load, for example:

Server Up Time: 23:16:12 up 625 days, 6:43, 0 users, load average: 0.00, 0.00, 0.00