I'm having the same issue with my RAZR MAXX. I have a combination of DLink 655 with DLink and Belkin access points. Never had and issue with my DX until I upgraded to the RM. I have no problem accessing the Facebook app with the 4G connection and no issue with any other site with the browser but if I try to access Facebook with the app or via m.facebook.com I get a timeout connection error lost connection. Very frustrating and no excuse.
I've tried changing channels with the APs and also change grom WPA only to WPA and WPA2 auto and still the same thing. If I check my DL speed with Speed Test, on WIFI I get consistently a pink of about 21ms, a DL spead of about 28,000 kbps and an upload speed of about 2100 kbps but no connection with FB app or even the FB mobile website. This is crazy.