you'll have to show us the procedure; the error itself is not descriptive enough to point out anything obvious.
the onlything i can offer is that if you are storing that decimal as a varchar, you'll have to double convert i think;
this returns the exact error you described:
select CONVERT(int,'12.80')
Msg 245, Level 16, State 1, Line 1
Conversion failed when converting the varchar value '12.80' to data type int.
select CONVERT(int,CONVERT(decimal(19,2),'12.80'))
Lowell