System Environment:
--------------------------

--Platform: i965

--Architecture(32-bit,64-bit,compatiblity): all

--2D driver:
commit 4a42b01f5ee5a673716d6959dfe0e693b037eb48 

--3D driver:
commit d7cf6a8a697a2fb4da171a36968f65aa0f108b27 

--Xserver:
commit 06c968acbf6771d5fed4b12ebd400fea791ea498 

--Drm
commit d6098db1409e8ee45052920d3acdd3b6f2cb80aa

--Kernel:
2.6.24-rc5


Bug detailed description:
-------------------------
this issue doesn't happen on i915
this issue doesn't happen in non-DRI mode

here some case means the following sequences:
1. enable, apply, and read back,  2 or more texture units separately, with GL_DECAL mode
2. then enable and apply 2 or more texture units together, with GL_MODULATE mode

but it turns out the result is incorrect



Reproduce steps:
----------------
1. start X
2. compile and run attached test case


Current result:
----------------
multiple texture units doesn't work as expected in some case


Expected result:
----------------
multiple texture units should work as expected