Several times last night, once again this morning on the same site.
Using VSD7 (build 24), Windows7 (64 bit), site is on SDrive. http://ccd.coffeecup.com/
This is popping up whenever I work with a block of 'Lorem Ipsum' text. I deleted a few lines and got the warning, then replaced some of it with my text and got the warning again, seems every time I go near it, it triggers an improper argument. The text box isn't overlapping or touching anything else (as in the past when this happened).
I'm going to try deleting it and typing a new paragraph to see what happens.
https://www.callendales.com