LotusScript Debugger on Linux

I wanted to debug Lotusscript on my VM Linux Box. The OS is Ubuntu 9.10 and the client is Notes 8.5.1.
When I switch on the debugger and step into the script, the debugger loses focus on every step, regardless if you use the mouse or F8.

Anyone else having the same problem? Not sure if it is a bug or if debugging is not supported or something else …