Strings all 'not set to an instance of an object' in Mono Debugger?

I never thought I'd be asking an 'Object reference not set' question, but with 3.4, when I'm debugging, ALL of my strings in C# files at least (not tried JS yet) are showing as 'not set' in Locals and Watch windows. They are getting set though, I can see that values parsed from them are set to the correct numeric values.

This makes debugging VERY challenging to say the least.

What happened? What can be done? Is it a bug? On the chance that it's a different install, my MonoDev version (about box) says Version 2.4.2