Hi Naineesh
The same kind of problem occurred in our project when we upgraded to BI 7.4. The issue was only in portal result. Not in RSRT or in analyzer. so we clearly found that it was an issue with Java.
In your case, how are you executing the query. Was it in Analyzer or in portal?
If its in portal, could you please check in analyzer or in RSRT to narrow down the issue.
Regards
Karthik