Nios 5.0 vs Quartus 6.0

I've build some projects in Quartus 5.0 Full Edition and Nios 5.0 IDE. Now I decided to change to Quartus 6.0 Web Edition. I've successfully generated and compiled a Quartus project and his SOPC system. However when I try to build the correspondent Nios project (in the Nios IDE 5.0) some errors are presented (my mutex components are not recognized and a src file called alt_busy.c (in /cygdrive/...nios2/components directory) presents some erros -- I don't have here the exacty error displayed in Nios IDE terminal). I've just tryied clean and rebuild my Nios projects, but the problems remain. Shall I necessarily install Nios 6.0?

Sorry if this question has already been answered.

Thanks!