I haven't seen this one before. Things you can try:
1. Uninstall connector software from all clients
2. Reinstall (or install) the latest version of .NET framework on clients and server
3. reboot all systems
4. Reinstall connector software on all clients from http://yourservername:55000
If this doesn't fix it you could try updating the BIOS of your server to the latest release. It sounds odd, however some users with similar errors solved their problem this way. If that also doesn't help try a server reinstall. Unless required please don't use any third party drivers (chipset, video and so on). If you are using SATA disks you can set them to run in IDE mode from the server BIOS before doing the reinstall. This way the system can use native WHS storage drivers.
Still not fixed? Please submit a bug to the Windows Home Server Connect Feedback site, instructions at the bottom of this page. If you don't feel confident with the suggestions above you can also start with submitting a bug. You may need to be a little patient, it can take some time before you get a reply.
