Hello Prakash,
Few checks:
> Open the query on Query Designer in order to be sure that no inconsistency is present on the query
> Run the transaction QCHECK
> If everything is fine, try to access the cube data under transaction LISTCUBE.
> If everything is fine, I do recommend you to run the ANALYZE_RSZ_TABLES (via SE38) and review all query definition tables of your queries.
Kind Regards,
Edward John