Ive seen a lot of issues with autostart... plus roaming between wifi and 3G / GPRS / EDGE etc etc.
Try taking it off autostart. Do you run from phone mem or MMC too??
The only time Ive had Fring stall on me was when my router was playing up... and yeah, I could browse the net, but it wasnt letting fring access.
Also... just in case you havent.. you could uninstall, turn off your phone, and then turn back on and reinstall....
Of course, if you have a list off issues you can send to Fring support open a ticket too.
Good luck.