I just got a Chinese smartphone, the THL W1+ (it has the MTK6577 CPU). Everything works fine except for texting. I can reply to texts fine, but if I try to send a text to a contact, I get an "invalid recipient" error (see attached picture). If I type in the number manually, however, it works fine. Other applications, like GO SMS and Handcent only work if I add the contact through their program; if I open up my contacts first, click on their name, and press send with GO SMS or Handcent, I get "invalid recipient."
I'm on AT&T in the US, too, and am using ICS 4.0.4.
Oh, and the phone is rooted, so any solution that requires root access is not a problem.