Whenever I use the Control Toolbox in the Excel user interface to
add a commandbutton to a worksheet, when I click the Font property
on the the property sheet for that commandbutton, it often freezes
and creates an Excel task, with no title, on the Windows Task bar
(not the Task Pane). This only happens with the Font property. :(

I have tried Ctrl + Alt + Delete to look at the Windows Task List,
which shows this task as 'running'.
The annoying thing is, although I can switch to other tasks in other
windows, I cannot do anything!
Mostly, I get sick of waiting, end the Excel task, lose unsaved
work, restart Excel and try again. The second time it may or may not
happen again!

Once I left this for about 15 minutes and when I came back I was
able to continue and change the font properties like size, colour,
etc.

Has anyone any ideas as to what is happening here, and how I can
prevent it?