RDP WinXP -> Win2k3 SP1 Data Encrption Errors

[Subi75]

I have staff who are doing RDP's from WinXP machines to Win2k3 SP1 servers (4 that I am aware of), and they have varying degrees of success on connection, where in some cases they cannot connect at all, or in some cases they can connect and log in for anywhere up to 2 hours before receiving Data Encryption errors, whereby they are then disconnected and can take a few minutes before they are then able to reconnect.
They are not using the latest RDP client from Microsoft, and FIPS encryption is not enabled on the Win2k3 SP1 servers.
Other staff in the same office are able to connect successfully for as long as they want.
One staff member, using a notebook, has told me that its even worse with the Data Encryption issues if he attempts to connect via RAS, rather then on the LAN.

NOTE - ALL Machines are on a corporate LAN environment. no firewalls or internet connection are between these users and the servers, although some servers are at a different corporate site to the users (but not all the servers which they are experiencing the issues with). Corporate network is an ISDN network between sites.

Any suggestions would be appreciated.

 

[Subi75]

Note of interest for this one... although no physical firewalls were involved, Zonelabs Integrity Flex firewall software was installed on some of the machines. In particular, all the machines affected had it installed. If it was disabled, they could connect to the RDP sessions without an issue.....

Anyhow, its been reassigned to our security people to modify the settings for Integrity Flex to allow RDP to the systems in question...