Verizon has identified the issue, pointing at the parentheses, and apparently have a patch in the works to correct it. We hear you saying that this is not always the case, and that the invalid message is coming up even without the parentheses. My sincerest hope that this patch, when it fixes the one problem, will knock out whatever is causing the glitch regardless of the contact. Rumored release is December 11th, will probably post about it later.
How to fix the Motorola DROID MMS bug November 15, 2009