I went through all the posts here on the forum
but none of the option which are listed are relavant to our situation.
they are all listed for BO 5.x version and we are using 6.5
and also the other production reports from the same universe,using same connection are refreshing properly
we are getting this exception error to only 2 reports ,and other 25 similar reports have no problem while refreshing.
If it is not too much work try to recreate those 2 reports from the scratch. It may happen that the report gets corrupted and the only way out is to recreate it.