Windows Server 2008 introduces a nice feature for the Terminal Services that is called RemoteApp. RemoteApp programs are accessed remotely through Terminal Services and appear as if they are running on the local computer. The RemoteApp is integrated on the client PC's desktop, running in its own resizable window and showing up in the taskbar. The big difference is that there is no Window of the Terminal Server's user desktop showing up any more. For more information on RemoteApp see: TS RemoteApp Step-by-Step Guide
The Dynamics AX Client is often executed on Windows Terminal Services especially if the available network bandwidth in the target location does not satisfy the minimum requirement needed.
When the Dynamics AX 4.0 Client or the Dynamics AX 2009 Client is running as RemoteApp on Windows Server 2008 Terminal Services, it might happen that you get an issue with Combo Boxes (Drop-Down elements). When you click at an item from a Combo Box with the mouse, the item you clicked at is not selected. You can however use the [Cursor Up] / [Cursor Down] keys on the Keyboard to select a different value.
This issue happens not with all Combo Boxes in the Dynamics AX Client, but it is often reported for the Print form when you want to change the target printer. The issue is also not limited to the Dynamics AX Client, but can also show up with other applications as well.
The Windows Hotfix KB968358 is solving this issue for the Remote Desktop Client 6.1. If you are using the Remote Desktop Client 7.0 on Windows 7 or Windows Vista please install the Windows Hotfix KB979425 instead (Note: There does not exist a fix for the Remote Desktop Client 7.0 running on Windows XP).
As the Hotfix is addressing the Remote Desktop Client it has to be installed on each Client PC that is accessing the Terminal Services hosting the Dynamics AX Client RemoteApp.