Sorry for not including the version, somehow forgot the top bug reporting rules. We are using 11.5. 64 and 32 bit.
Attached is the file, although I suspect it won`t help reproduce the problem, it is pretty clear as soon as you add some chars to the script.
We have seen this on several PCs and different versions of SQL-Yog, so it is not just one particular setup.
I hope you can reproduce it, if not though, I know to avoid using now.