Applying Service packs and patches are really needed as they resolve most of the issues. SAP has already released many SP for 4.0 and patch to upgrade to 4.1.
You can upgrade to 4.1 SP1 directly from 4.0 SP4 version and then also apply SP2 for 4.1
Just in case you want to troubleshoot, please revert and our forum members can help with multiple suggestions on the same.
Message was edited by: Arvind Pandalai