My new breakpoint code is coming along really good :-)
Yesterday, I got all the required features working so I started testing. The good news is that this code actually works - multiple appdomains and generic instances are working just fine :-)
The longer I'm working on this, the more problems I find in the old symbol table code. There is, for instance, a piece of code which never worked for the past 2 years - but nobody ever noticed because it can only be triggered if you run a really, really huge application with ---debug. I only figured it out by accident while I decreased the limits to do some performance testing. There are also race conditions when we need to start a new symbol table since the debugger might currently be reading it.
However, this shouldn't be too bad - I already have some really good ideas which'll not only increase stability but also performance.