I had the same problem as qhavenga - just doing standard Nios stuff - no uClinux.
Error message when compiling a simple Nios application:
8055439 [main] nios2-elf-gcc 16516 fork_copy: linked dll data/bss pass 0 failed, 0x576000..0x576264, done 0, windows pid 16700, Win32 error 487
The article
http://www.cygwin.com/ml/cygwin/2006-01/msg00782.html (
http://www.cygwin.com/ml/cygwin/2006-01/msg00782.html) suggests that there is a conflict with the "Logitech Process Monitor" service and cygwin.
After un-installing my Logitech camera (QuickCam Pro 5000) driver/appl. SW and re-installing Nios IDE - the problem was gone.
http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif
Regards,
Ove Brynestad