Lars, When the hang occurs have the user do - Start - all programs - Lotus applications - support - then :
Collect Lotus Notes diagnostic data and leave Notes running , when this is complete then run it again. then
Collect Lotus Notes diagnostic data and exit Notes
you can collect all the data under folders below and send them to IBM Support with the steps to reproduce if possible
Notes\data\workspace\logs
Notes\data\IBM_TECHNICAL_SUPPORT