O.K this confirms that you can access the with the sysman/oem_temp and the readings confirms that the OMS is active. Now can you connect to your OEM on the solaris box using

$oemapp console &

give the same user name and password and see whether you were able to get the console gui. Once you are sure about this
then on the NT application, give this solaris box's host name and the same user name and password and try connecting to the solaris system. If that does not go through, do

ping solaris_hostname.domain

and see whether you are able to make connection to it. In the mean time, you got to be sure that you are running the same version of OEM as that of the solaris one.

Let me know of if you have any problem.
Sam