Microsoft has issued an alert explaining why users have seen problems when connecting ActiveSync 4.0 with new Windows Mobile 5.0 devices. The page also lists steps to prevent these problems happening.

Specifically, some users of ActiveSync 4.0 have reported challenges when using the USB connection of their personal computer to connect to a device with Windows Mobile 5.0. In many cases, these challenges are likely caused by interoperability with desktop firewall applications or applications that manage network traffic. These applications appear to conflict with the TCP traffic between a device and the PC.

An update for ActiveSync is scheduled to be available in late November, but customers may also resolve the issue manually immediately by visiting the Microsoft Windows Mobile website.

This issue only affects people with new devices just coming to market and running Windows Mobile 5.0 software, and only when synchronizing directly to a PC when using a USB connection (wireless synchronization via Bluetooth, infrared or directly to a server or other services are not affected).

In Asia-Pacific, the devices affected are the i-mate JasJar, i-mate K-Jam, i-mate SP5 and i-mate SP5m.

In Europe, these devices include the Orange SPV M5000, iMate JasJar, iMate K-Jam, T-Mobile Vario, T-Mobile MDA Pro, O2 XDA Exec, O2 XDA Mini S, O2 XDA Phone, FSC Pocket LOOX N500, Dell Axim X51, Dell Axim X51v, HP PPC series (rx1950, hx2190, hx2490, hx2790).