Apache not starting after upgrade to OpenSuse 12.1
Start checking the logfile of the apache, especially the error log. Eventually raise the LogLevel directive. You might simply miss an active module, library or dependency for the server to start.
Update: Your problem is caused by the upgrade. Opensuse switched from sysvinit to systemd as you can read here: link. You can read up on the issue in the bugreport: link.
The workaround: is to install the sysvinit-init package. As soon as its install gets acknowledged the removal of the systemd-sysvinit package will be suggested.