The errors that you have pasted are not sufficient to come to any conclusion. Is this the first time you are installing EM or you have tried it few times? Look for more error in the log: /home/oracle/srv/ora/Middleware/oms/cfgtoollogs/omsca/omsca_20130225132822.log
Is your DB and EM on same host? Does it have enough RAM / Hard disk?
It’s best if you can open an SR with oracle support and upload all the logs.