Daz tests products in Poser 5, and it wouldn't pass QA without it working, so he should work fine.

Open the M4 cr2 in notepad, and in the first line or two, you'll see "version" and a number.. probably  6 or 7. (That refers to the poser version number)

Change that number to 5, and then resave that cr2 as M4Poser 5.cr2

Load that into P5, and see if it works.

Since Poser 6 is on sale for only $30 at CP, why not snag that as a cheap upgrade as well?

Way too many people take way too many things way too seriously.