It's a bit likely a excel error :), Is it your report is an excel document?
if not, maybe you can find line of essbase.properties like
increase the number then restart service and try.
Internal Error : query is too large and cannot execute
if its report script which you trigger from EAS
i guess you can breck the scripts in to 2 or 3 or 4 parts and run them
like if ur selecting all accounts go one by one and see the diffrence