I have an 8300 I have just upgraded the firmware to the latest one according to this sticky.
I get this error message every time I try to send a text message;
uncaught exception java.lang.IllegalArgumentException
I go into menu then click on text/media messages then it asks if I want to [use once] or select a contact. Whether I pick [use once] or select a contact I get that error message thrown. It happens every time.
I can make and receive calls no problem.
I have had the phone unlocked, it was originally locked to Vodafone UK.