We have various users in different locations using Citrix to access a corpore-wide database (Microsoft Access), and some of them have experienced a total PC lockup while running Citrix at the same time as running other applications on their local PC. This is especially true for our CAD users that run Bentley's Microstation CAD at the same time as Citrix. Ctrl-Alt-Delete doesn't do anything when this occurs. They have to cold restart their PCs. They can run for days in the local applications w/o trouble, it's just when they are using Citrix that the lockup problem occurs.