I sent a bug report from my Account too. But I want drop a line here too.
I tried to make a Silverlight4 Bussiness App (SL4RCm WCF RIA RC, RIA TOOLKIT).
The empty project was build ok first time, but after that it cannot be build anymore. It seems that JustCode and RIA toolkit code generators are clashing. The code generator cannot access the generated_code folder and justcode start reporting some bogus errors. Eventually the whole IDE will crash. Screenshot and log files are included in bug report. I was forced to uninstall JustCode for now because that.
BTW I tried the last stable version and the last internal build.