So you are using pretty new libdrm but a bit older xf86-video-intel/xserver.
Could you upgrade to xf86-video-intel >=2.7 (preferrably master branch tip) and xserver>=1.6, and better try UXA (instead of EXA)? EXA has been removed in 2.7.99. 

Yes, I had troubles of X being stuck in an infinite loop with this configuration :
X.Org X Server 1.6.1.901 (1.6.2 RC 1)
Intel driver 2.7.1

But this problem is gone, about the inifinte loop, I have this messages in Xorg.0.log :
[mi] EQ overflowing. The server is probably stuck in an infinite loop.

Backtrace:
0: /usr/bin/X(xorg_backtrace+0x26) [0x4ead06]
1: /usr/bin/X(mieqEnqueue+0x291) [0x4cb751]
2: /usr/bin/X(xf86PostMotionEventP+0xc4) [0x4765d4]
3: /usr/bin/X(xf86PostMotionEvent+0xb1) [0x4767b1]
4: /usr/lib64/xorg/modules/input//synaptics_drv.so [0x7fb8fd249b42]
5: /usr/lib64/xorg/modules/input//synaptics_drv.so [0x7fb8fd24c16c]
6: /usr/bin/X [0x4893a5]
7: /usr/bin/X [0x46d2b7]
8: /lib/libpthread.so.0 [0x7fb9130913c0]
9: /lib/libc.so.6(ioctl+0x7) [0x7fb911049117]
10: /usr/lib/libdrm.so.2(drmIoctl+0x23) [0x7fb910342c23]
11: /usr/lib/libdrm.so.2(drmCommandWrite+0x1b) [0x7fb910342eab]
12: /usr/lib64/xorg/modules/drivers//intel_drv.so(I830Sync+0xa8) [0x7fb90f822988]
13: /usr/lib64/xorg/modules//libexa.so(exaWaitSync+0x5c) [0x7fb90efbbc2c]
14: /usr/lib64/xorg/modules//libexa.so(ExaDoPrepareAccess+0x91) [0x7fb90efbcde1]
15: /usr/lib64/xorg/modules//libexa.so [0x7fb90efc21a9]
16: /usr/lib64/xorg/modules//libexa.so [0x7fb90efc26ad]
17: /usr/lib64/xorg/modules//libexa.so(exaDoMigration+0x68f) [0x7fb90efc2e9f]
18: /usr/lib64/xorg/modules//libexa.so [0x7fb90efc431c]
19: /usr/lib64/xorg/modules//libexa.so(exaComposite+0x63f) [0x7fb90efc4a3f]
20: /usr/bin/X [0x52bfa8]
21: /usr/bin/X [0x51b1ca]
22: /usr/bin/X(Dispatch+0x364) [0x44a084]
23: /usr/bin/X(main+0x44d) [0x43079d]
24: /lib/libc.so.6(__libc_start_main+0xf4) [0x7fb910fa84a4]
25: /usr/bin/X [0x42fb89]
[mi] mieqEnequeue: out-of-order valuator event; dropping.
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
<Snip>

but I don't know how to reproduce that...

Ho right, switching to UXA, I'll do that :)
It should avoid those X freezes....

Ok, still in th same area, I got an X server crash with that message :
Mesa 7.4.2 implementation error: invalid reference to a deleted texture object
Please report at bugzilla.freedesktop.org
X: main/texobj.c:305: _mesa_reference_texobj: Assertion `valid_texture_object(oldTex)' failed.

I was changing some kde eye-candy effects. the server restarted and know, it works fine with the effects enabled.

Should I create another bug report for this ?


FYI :

Distribution : Gentoo

uname -a
Linux naboo 2.6.30-rc8 #8 SMP Wed Jun 3 15:37:48 CEST 2009 x86_64 Intel(R) Core(TM)2 Duo CPU T8300 @ 2.40GHz GenuineIntel GNU/Linux

pkg-config --modversion libdrm
2.4.11

OpenGL renderer string: Mesa DRI Intel(R) 965GM GEM 20090418 2009Q1           
OpenGL version string: 2.0 Mesa 7.4.2

X.Org X Server 1.6.1.901 (1.6.2 RC 1)
Release Date: 2009-5-8

(II) Module intel: vendor="X.Org Foundation"
        compiled for 1.6.1.901, module version = 2.7.1

LVDS connected 1920x1200+0+0 (normal left inverted right x axis y axis) 331mm x
207mm
   1920x1200      60.0*+   60.0     58.9

(In reply to comment #4)
> Ok, still in th same area, I got an X server crash with that message :
> Mesa 7.4.2 implementation error: invalid reference to a deleted texture object
> Please report at bugzilla.freedesktop.org
> X: main/texobj.c:305: _mesa_reference_texobj: Assertion
> `valid_texture_object(oldTex)' failed.
> I was changing some kde eye-candy effects. the server restarted and know, it
> works fine with the effects enabled.
> Should I create another bug report for this ?

Yes, please file a separate bug report, as this shows a mesa error.

And I'd close this one if you don't pursue for EXA (which has been removed from master branch).