Problem with an old library not available anymore on testing

After an update, begins some problems with lixcb-xlib.so.0 that
doesn'r exits anymore on testing. I suppose is my fault having some
repositories in lenny rather than testing. But I couldn't resolve it,
lots of apps ask for that library, including X server errors. Last log
in kdm.log says:

-:0: symbol lookup error: /usr/lib/libxcb-xlib.so.0: undefined symbol:
_xcb_lock_io
error setting MTRR (base = 0xc0000000, size = 0x10000000, type = 1)
Invalid argument (22)

if I run startx, see the cursor but nothing else. Everyother Xwindow
app doesn't init.

I tried reinstalling each package, but still no luck.

Somebody know how to avoid using that old library?

Thanks!
Guillermo