Error in calling RFC function module

Hi,

I have created one simple WebDynpro application in which i am calling a RFC function module. it was working fine then i had to make changes in interface of function module. After making changes i deleted and recreated the RFC model and readjusted all context mappings. But now when i try to run the application i gives an error

"Could not create JCO connection with logical system :default".

Can any one tell me what could be its reason.

Thanks,

Komal.