Database Conundrum

This error is bugging me:

Operand type clash: nvarchar is incompatible with image

It happens when I try to submit a complex form. Problem is, I don’t know which field is causing the error. Not much on internet, probably just sending the wrong datatype. Debugging time!

Update: No easy fix for this one. There are some similar cases here and here, but nothing that’s quite the same. Still don’t know which field is the problem. Seems like it has something to do with nulls, as those links say.

Update 2: Fixed it! Problem was with datatypes agreeing between page code, stored procedure and table design. (stored procedure had image, other two were varchar).