This error will occur when using an earlier version of the clientshell.exe on the Treo 700 device. You need to be using the 6.5.7.5 clientshell.exe version. Please hard reset the device and then to get the correct version for the WSES product you can go to
http://ota.wsync.com/wses64/ and download the Treo 700w WSES client. Users of the Wireless Sync product should hard reset their devices and go to the Wireless Sync Application. This has a stub that will point to and download the newer client. Updates may be made to this in the future, so to correct this issue you should be running at least the 6.5.7.5 version. This error occurred during the synchronization of Calendar events. Users who downloaded the client prior to this release may experience this issue.
-Intellisync Support