The repository is started and on my local server. I am able to connect via sqlplus with and without service name.
The event viewer does not have too much details. I have cut and pasted some info from oms.nohup. Please take a look below.

OEMCTRL for Windows NT: Version 2.2.0.0.0
Copyright (c) 1998, 2000, Oracle Corporation. All rights reserved.
Starting the Oracle Management Server... [main][2003-9-2:9:20:11:688] VdbSession.processError: errorCode >12154<
[main][2003-9-2:9:20:11:688] VdbSession.processError: errorMsg >ORA-12154: TNS:could not resolve service name
<
[main][2003-9-2:9:20:11:688] VdbSession.processError: database connection error

VXA-2018 :
Unable to connect to OMS registry serviceoracle.sysman.vxn.VxnBootstrapException:
at oracle.sysman.vxa.VxaAppServer.startServices(VxaAppServer.java:1353)
at oracle.sysman.vxa.VxaAppServer.main(VxaAppServer.java:2547)

Error starting Oracle Management Server. OEMCTRL for Windows NT: Version 2.2.0.0.0
Copyright (c) 1998, 2000, Oracle Corporation. All rights reserved.
Starting the Oracle Management Server... [main][2003-9-2:9:20:38:186] VdbSession.processError: errorCode >12154<
[main][2003-9-2:9:20:38:186] VdbSession.processError: errorMsg >ORA-12154: TNS:could not resolve service name
<
[main][2003-9-2:9:20:38:186] VdbSession.processError: database connection error

VXA-2018 :
Unable to connect to OMS registry serviceoracle.sysman.vxn.VxnBootstrapException:
at oracle.sysman.vxa.VxaAppServer.startServices(VxaAppServer.java:1353)
at oracle.sysman.vxa.VxaAppServer.main(VxaAppServer.java:2547)

Error starting Oracle Management Server. OEMCTRL for Windows NT: Version 2.2.0.0.0
Copyright (c) 1998, 2000, Oracle Corporation. All rights reserved.
Starting the Oracle Management Server... [main][2003-9-2:9:20:56:282] VdbSession.processError: errorCode >12154<