error getting while running the published report

HI,

I am getting error : An internal error occured while calling 'getSessionInfosEx' API. (Error: ERR_WIS_30270) (FBE60502) whenever scheduled/published report being run from 4.0 BO Scheduler.

ITS a webi report and was running fine from BO 4.0 scheduler.

But since last 2 days the report is failing giving error "An internal error occured while calling 'getSessionInfosEx' API. (Error: ERR_WIS_30270) (FBE60502)".

Solution : I restarted the webiprocessing server : the report ran successfully but again  when the report runs next day : same error being encountered .

CAN SOMEBODY PLEASE SUGGEST A PERMANENT SOLUTION PLEASE ?

Regards,

Ranjeeta