Hi,
Please check the following .(since it is a datatype mismatch)
1: First thing check your parameter datatype .May be that will be different from your front end datatype.
2: Please check the database field data type.
3: Please check whether you have mentioned the length of your parameter in the parameter tab.

4: Please check the parameter return type.

I hope after checking all these thing it should work.

Thanks
Karun