[MonoDevelop] How to step in to Mono source code?

[IBBoard]

Hi,

I'm having a bit of a fight with GTK# and I want to step into the source 
code to see what it is doing. I do it all the time in my day job using 
Java in Eclipse and it can be hugely useful. I know it is possible, as 
I've suggested it as a feature and been told that it already exists in 
MonoDevelop and I just needed to untick a "only step into code in local 
projects" box in the preferences.

I've just installed mono-core-debugsource (after already having 
-debuginfo) on openSUSE 11.3 and restarted MD, but if I step into 
anything like Dictionary or any other core classes then I still just get 
the stacktrace updating but the arrow staying where it is and turning 
green to show that it is in inner code.

Am I missing something? Can someone give me some pointers on how to step 
into Mono's code as well as my own?

Thanks,

IBBoard