I'm trying to customize my BackTrack4 image so I can use the live disk with my ati graphic card. While trying to put the drivers with the apt-get install ati-driver command, I get the following message:

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.
Need to get 0B/17.8MB of archives.
After this operation, 86.0MB of additional disk space will be used.
(Reading database ... 233992 files and directories currently installed.)
Unpacking ati-driver (from .../ati-driver_9.5-bt2_i386.deb) ...
Replacing files in old package libgl1-mesa-glx ...
Replacing files in old package xserver-xorg-core ...
dpkg: error processing /var/cache/apt/archives/ati-driver_9.5-bt2_i386.deb (--unpack):
trying to overwrite `/usr/lib/libGL.so', which is also in package libgl1-mesa-dev
Processing triggers for man-db ...
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

I tried everything that I could find searching the net, but I couldn't solve the problem. Does anyone have an idea how to solve the problem?