S1+S3 sounds right. Your BIOS is probably already configured correctly, since the computer will sometimes enter hibernation and resume.
My first thought is that your PSU is cutting all power before the hibernation file can be fully written.
I would try extending the time before the P2140 does a hard off and see if that resolves the issue.
Additionally, less RAM may help the situation, since the hibernation file is the same size as your physical RAM. If you're running 4GB, reduce to 2GB and see if hibernation/resume is more reliable.