I can't easily reproduce the problem since I don't use X.  Perhaps the 
problem is due to cleanup changes in src/unexaix.c.  To test this 
hypothesis, can you please try the attached file in place of the 24.3.91 
src/unexaix.c?  The attached file is as close to 24.3's unexaix.c as 
possible; the files can't be identical due to other changes in Emacs. 
Thanks.