Hi Rahul,
Just saw your mail and analyzed that report may be build in 0n 10g version and while you are trying to open in 6.0.8.8.3 which is lower than the 10g.
If you try to open higer version object into lower version always you get'll such expirence.
Try to get 10g and open and I'm quite sure the issue will get resolved.

Cheers!!!
Feroz Malik