Hi,
I've the same problem.

I already done the actions below:
1. turn off firewall;
2. there is no other application using 48000 port, just Nimsoft Controller;
3. telnet command and it works.
4. restart all the probes
5. validate the probes
I also check the logs and there is no errors, just on controller:
Aug 26 01:05:47:346 [1812] Controller: hub ALS-NIM-MONS1hub(192........) NO CONTACT (communication error)
Aug 26 01:05:48:360 [1812] Controller: hub ALS-NIM-MONS1hub(192........) NO CONTACT (communication error)
Aug 26 01:05:49:374 [1812] Controller: hub ALS-NIM-MONS1hub(192........) NO CONTACT (communication error)
Aug 26 01:05:50:388 [1812] Controller: hub ALS-NIM-MONS1hub(192........) NO CONTACT (communication error)
Aug 26 01:05:51:402 [1812] Controller: Hub ALS-NIM-MONS1hub(192........) contact established
Aug 26 01:05:51:402 [1812] Controller: primary hub changed name to ALS-NIM-MONS1dom/ALS-NIM-MONS1hub/als-nim-mons1
Aug 26 01:05:51:402 [1812] Controller: temp hub changed name to ALS-NIM-MONS1dom/ALS-NIM-MONS1hub/als-nim-mons1
Aug 26 05:06:02:764 [1812] Controller: Hub ALS-NIM-MONS1hub(192........) contact established
Do you have any suggestion with more actions to do?
Thanks,
Alex