since you didn't get a reply here i'd suggest opening a support ticket.
What is the version of portal you are using? Also log file is called bsm.log and can be found in BladeLogicPortal/portal/logs/bsm.log, I would follow same recommendation Bill made to open a case and attach log file to the case as we do not review logs over communities due to sensitive information they might contain.
thanks for replying.
We already raised the ticket.
The problem was I was using IE for login. It was a known issue (QM002395421) with IE. Tried with google chrome and was able to import the file without any error.