If you have issues with the new IGEL Linux V5 and none RemoteFX capable Remote Desktop Services (Windows 2008 and older or Windows 7 without SP1 and older) you can fix the issue in two ways:
1) In RDP->RDP Global disable RemoteFX (similar for sessions if the global configuration is not used)!
2) or enable the Legacy RDP Client in RDP->RDP Global->Option, make also sure that RemoteFX is disabled!
If you not perform one of these steps a connection from the client can have a impact for all connected RDS Users (EventID 1503 and other on the Server). Please note that the new IGEL Remote Desktop Service Client is not really designed to work with such old systems like Windows 2003 or similar!
RemoteFX capable are: Windows 2012 (incl. R2), Windows 8 (incl. 8.1), Windows 2008 R2 and Windows 7 SP1, RemoteFX needs to be enabled/configured thru Policies! Windows 2008 R2 in general can not use RemoteFX USB Redirection and a Windows 7 SP1 VM needs to have a RemoteFX GFX Adapter assigned in the Hyper-V console to redirect USB devices. USB Redirection means USB Port to Server redirection and not Printer or USB Memory mapping, only to be clear here... :-)