compiled mesa again from master git branch (tree   
7cbc1aafe166dd925c5626c7118f523c8b75ae6d) and got this in dmesg
[    9.917097] glxinfo[2482]: segfault at 0 ip           (null) sp
00007ffffc441708 error 14 in glxinfo[400000+6000]
in the end, xbmc doesn't show up

i went back to mesa-9.0.2 and linux-3.8.0-rc5
also here, the Xorg.0.log is spam the whole time with flip errors

the same is with linux-3.7.4 and mesa-9.0.2
i never had a look at my Xorg.0.log when i was using linux-3.7.x and mesa-9.0.x
hmm ... the log-spam was always there?

so what is causing to spam the Xorg.0.log with these flip errors?