Does it produce an error?

(and what is the 1 between the fromuser and touser part)?
Just as a thought: Is that imp command you show exactly the command you run from the script, or is the username/password, for example, in a variable? If so, did you export the varaible?

The exit isn't neccessary either in the SQL*Plus or the script. You should replace it with a / in the SQL.