Hi,
Note down the error message details and put a break point in new debugger by providing the message details (id,number and type).
please activate the update debugging as well while debugging because if error occures while updating then it iwll stop or else it willnot stop even though you put breake point at message.
or try one more method that open message in SE91 tcode then try where used list from there and put break point an debug. some times it will not work(if they are generating dynamic message ).