I do not think the patch level has something to do with this failure.
Most of the times I have seen this problem it is due to:
1. Another service running on port 5555 on the client. You can check this with netstat -an | strfind 5555.
If there is such service the telnet will still return HPE INET, but the import will fail.
In other words: telnet localhost 5555, telnet <Other host> 5555 executed from both CM and clinet should return HPE INET. This is a proof the service is running and listenning on the port.
2. Hostname resolution - DP is very sensitive to this. Check if the CM and the client resolve each other by FQDN - from both execute: ping <FQDN of other host>. If the ping does not work put a record in the hosts file in the following order: <IP> <FQDN> <Short name>. Even if the hosts are resolved with DNS server DP will check the hosts file if the DNS resolution does not work.
3. It is not clear if this is the only Windows host in the cell, but if you have a Windows Installation Server, try to "Add" instead of "Import". Adding will run an installation session with messages and will give you some idea about the error. Import does not print any messages.
4. Finally DP keeps the name of the Cell Manager in the registry and you can check if it properly put. Very often I have seen the Error: Client is already member of another cell due to the hostname resolution (cell manager resolved by shortname instead of FQDN). On the CM execute: omnidbutil -show_cell_name and make sure it is the same on the client in: regedit - HKEY_LOCAL_MACHINE - SOFTWARE - Hewlet-Packard- OpenView - OmniBackII - Site.
What I would do is to uninstall the DP from the client and install the client locally. During the installation process you can put the name of the CM and check if it responds. But hostname resolution should work and it is the reason for such failure in 99% of the time.
If nothing helps you can try to check the debugs yourself: execute: omnicc -import_host <HostnameOfClient> -debug 1-500 import.txt
Check the debug directory which is by defaul - for UNIX /tmp and for Win Program Data\Omniback\tmp (I do not think there will be something on the client, but check it anyway).
Search the debugs for the error you are getting and scroll up a bit to hopefully find the reason.
DP 7.xx is not supported for a long time now so swithing to 9.xx will be a good idea.
Good luck.