i810 crashes when switching bewteen X and text console

Hello,

I've found a problem with XFree 4.6 on the Dell Optiplex GX110, which has
an Intel i810E graphics chipset (i810 module). It worked well in XFree86 
4.5.

X startx normally, but when switching back to text console and again to X 
server,
the screen becomes dark and the text consoles become unusable too.
The system doesn't crash and I can see this in /var/log/XFree86.0.log

Fatal server error:
EnterVT failed for screen 0


When reporting a problem related to a server crash, please send
the full server output, not just the last messages.
This can be found in the log file "/var/log/XFree86.0.log".

Error in I810WaitLpRing(), now is 61278, start is 59277
pgetbl_ctl: 0x1bc0001 pgetbl_err: 0x0
ipeir: 0 iphdr: 0
LP ring tail: 8 head: 0 len: 0 start 0
eir: 0 esr: 0 emr: 3d
instdone: ff7b instpm: 0
memmode: 4 instps: 0
hwstam: 9ac7 ier: 0 imr: 9ac7 iir: 0
space: 65520 wanted 65528
(II) I810(0): [drm] removed 1 reserved context for kernel
(II) I810(0): [drm] unmapping 8192 bytes of SAREA 0xc89e2000 at 0x4061c000

FatalError re-entered, aborting
lockup


The following lines can be found in the dmesg :

[drm] Using v1.4 init.
[drm:i810_wait_ring] *ERROR* space: 65512 wanted 65528
[drm:i810_wait_ring] *ERROR* lockup
[drm:i810_wait_ring] *ERROR* space: 65504 wanted 65528
[drm:i810_wait_ring] *ERROR* lockup
mtrr: base(0xf8000000) is not aligned on a size(0x180000) boundary


The only solution I found to avoid it was this option for the i810 device 
:

Option "DRI" "no"

I noted this problem with XFree 4.6.0 + patches 1-7.

Loïc, Toulouse, France