Python Exception Occurred

Traceback (most recent call last):
  File "/home/rizwank/geekymedia.com/viewcvs/lib/viewcvs.py", line 2625, in run_cgi
    main()
  File "/home/rizwank/geekymedia.com/viewcvs/lib/viewcvs.py", line 2603, in main
    view_diff(request, full_name[:-5])
  File "/home/rizwank/geekymedia.com/viewcvs/lib/viewcvs.py", line 2371, in view_diff
    fp = popen.popen(os.path.normpath(os.path.join(cfg.general.rcs_path,'rcsdiff')), args, 'r')
  File "/home/rizwank/geekymedia.com/viewcvs/lib/popen.py", line 33, in popen
    pid = os.fork()
OSError: [Errno 11] Resource temporarily unavailable