Hi,
I had the similar problem, but i tried to work out a way where i dont miss the SMS which was there in my inbox.
For this you need the sms.db and the sqlite program as well as little knowledge writing SQL queries. Export the sms.db to your PC.
open sms.db using sqlite
and then execute this command in sqlite after opening the sms.db
SELECT * from messages;
Once you execute the above command you will see all the message as well as the junk message which is obstructing the sms app to open. Note down the ROWID of that message.
DELETE * from message where ROWID=<No you have noted down>;
repeat the above step for all the junk messages. Then quit and exit.
Copy the sms.db to the same location on your iphone. You will have all the messages excluding the junk and your sms app will open also

.
Regards,
Francis.