Having the same problem as most other people here. Internet is fine, sending picture messages is fine, cannot receive picture messages. I'm using a Galaxy S2. Ported my number over from AT&T Gophone. Tried many, many APN settings with no luck.
I tried GoSMSpro as some have suggested (while using the Straight Talk recommended APN settings) and that actually did work. I also noticed that while it was installed, the stock messaging app seemed to work as well - I was able to receive photo messages with both.
As a test, I uninstalled GoSMSpro to see if the stock app would continue to work - and no. The problem returned.
Can anyone explain to me why this is the case? It would seem to me that this must mean that GoSMS changes or works around some setting on the phone. (It does not change any of the APN settings - I looked at that).
I know the obvious solution here is to just keep using GoSMS. And yes, I'll do that. But, I kind of hate it. It's just a big, clunky app that pops up ads, and I have no need for all the icons and such. It's better than the non-working stock app, of course - but I would still much prefer the stock app if I could get it work.