I assume there is an sms in the sim card that cause this error. To able solve the error i need more detail about the sms, ex its type and content. I need your help to identify the sms.
Until we can find the exact problem, perhaps you want to use this initial command (put it in terminal's setting):
AT+CMGD=0,4
The command will tell the modem to delete all smses in its simcard. So the sms cause the problem can be deleted, but come with consequence that it will delete other smses.
If you can sniff the COM port and send me the log, it will be very helpful.
I hope this will help.
sorry for my bad English.