BF Mobile Failure on Nokia E72 - pls help

I happily ran BF Mobile on my Nokia E72 under my O2 contract. I recently ended the contract and changed to pay-as-you-go and transferred my number to a new SIM card.
Since then I can't access the app and get an error message "27" comes up.
I have already uninstalled and re-installed the app, but no joy.

Thanks in advance.