LSMW+IDoc to transfer Merchandise Category?

Hi, Gurus,

anyone has migrated merchandise categories by using LSMW + IDoc method?

I used message type: W_WGRP and Basic Type W_WGRP01.

But I got always error message: Class XXX does not exist or or is not valid on this date.

Import Method: IDoc or BAPI (I tried these two methods, same prblem. but it works by BA-Recorder. I'm confused)

What for a problem? anyone met the similar problem?

highly appreciated for the supper!

Regards

Kefei