Unable to establish a secure session with the remote computer (-5)

Hi there.

We are using 9.5.

Very regulary when we try to remote to computers we get the following message Unable to establish a secure session with the remote computer (-5)

I have researched this myself and I have checked quite a few things. We have checked that the ports :9595 are open.

This is on a corporate network where all machines use the same agent and use the same firewall, yet only some of the computers have this issue. Has anyone come across this?

Thanks

Mike