I know SQL SP3 has added a bunch of new error messages for things we were all blissfully unaware of before. This looks like one of them. If this is taking your server down, you can look into the fix on KB article 818897.
That's where I started, but realized that this patch eliminates the AV, not the fact that the proc will fail anyway and the error will sill post.
I found a similar issue raised in ms sqlserver news group, where they had a declaration discrepancy between a passed NVARCHAR param and param definition in the proc (VARCHAR). Once they mirrored the definitions the error disappeared. In our case there is nothing to change, on both sides the parm declared as TEXT (or so my developers say it is on FE). Of course, I'll make sure they're not "exagerating" , but the fact stays for now, - TEXT = TEXT.