Strange Behaviour of R/3 Systems

Hi,

I have a Webdynpro application, where in i m fetching some data from 3 different R/3 systems depending on selection using an RFC.

For first System RFC, In debugging, F5 for RFC code takes me to that system and i can debug in that system.

But for other systems, its not behaving that way, F5 comes out of RFC behaving similar to F6.

Can anybody tell me what might be the reason for these strange behavior of diff systems? What myt be missing or is there any thing related to System configuration?

Thanks,

Tejaswini