And another (with issue2636-20101030.zip):

$ cat test.py 
import re, regex
text = "XYABCYPPQ\nQ DEF"
regexp = 'X(Y[^Y]+?){1,2}(\ |Q)+DEF'
print re.findall(regexp, text)
print regex.findall(regexp, text)

$ python test.py 
[('YPPQ\n', ' ')]
[]