Good work in finding the steps to produce the problem. I have fixed it in my copy and the fix will be in svn trunk by late tonight.
I sent Diego a script to alter a stored procedure which will fix it immediately for MS SQL. Unfortunately since the MySql sql statments are embedded in the WebStore.Data.dll, it will be fixed in the next release, I can't provide a script to fix it.
I will try to get a bug fix release out soon.