I read the solution at the top of the page, it seems odd that buying a battery saving app would help any, but hey if it works, it works.
I've seen one or two other threads like this. But unfortunately I don't know of a solution other then the one at the top of the thread, which I hope people have tried. My best guess is you have an app that's causing an issue with your MMS. I would try a factory data reset if you haven't already. If that doesn't work then a hard factory data reset may be in order. Then you could start adding your apps in one at a time to see what is causing the problem.
I've never had an issue with an MMS and just from the response on this thread which started in January I don't think this is an issue affecting most people. I think your issues are real - but it's something in your Droid causing a problem.
So try the solutions given and let me know if anything works. Good luck.
I finally got an MMS to go through yesterday. Don't know if this made a difference but after reading about the () problem in old posts, I manually entered the number and it succeeded. I had tried to send an identical message a few minutes earlier and failed multiple times but this was using my contact list. YMMV.