“more” tag on user access manager

hello,
I’m using user access manager plugin.
one of it’s options is that only registered users will see the content after the “more” tag.

I’m using wordpress mu. can that be a problem that it doesn’t work?
anyway, I can see the title and the description and then comes the “more” text (which I couldn’t find yet from where it takes it)

when pressing on the “more” then I get “undefined” instead of the rest of the post.

does anybody knowhow I can solve to problem?

thanks,
Shlomo