I'm sure you've researched and found some weird accounts of people removing the micro sd card and it working again....this seriously makes no sense to me, whatsoever. But I removed mine,and rebooted phone. Before I did that, yesterday I uninstalled any apps I installed recently (I learned that some apps can mess with the wifi). It actually turned on right after reboot, but then it went away again....
So far, my wifi is up and running just fine. It also turned on last night, but in the morning was gone--this was before I removed the sd. Anyway--TRY IT! So, uninstall any apps you installed before this started happening. See if that does anything. If not, remove your microsd card.
Check this out http://support.t-mobile.com/docs/DOC-3356
If the issue is still ongoing then please use the online chat http://support.t-mobile.com/community/chat or call in for further support.
I know this has been a headache for you guys. Thanks for being patient.
Have a great day and thanks so much for posting