Comination chart issue in cognos11

[sunny bachan prasad]

Hi,
We have recently migrated to cognos 11 and facing issuse with combination chart. We have a report which consist of combination chart and it is running fine in  Cognos 10. But same report in cognos 11 is throwing erorr as "INTERNAL QUERY SERVICE ERROR HAS OCCURRED". In combination chart we are using three data item in series primary axis in which 1 value is bar graph and other two are for  line graph. Report is running fine when i am uisng 1 data item for bar and line but when i am using 1 data item for bar and other two for line graph then above error is coming. I checked query it is working fine and able to generate tabular data as well. Can anyone share his/her experience on this?

Thanks in Advance.