How to downgrade a package on debian etch?

[Mark Phillips]

There seems to be a bug in rdesktop that causes a segmentation fault quite 
often, which makes the program hard to use. In the Debian bug tracking 
system, it has been traced back to an upgrade of the package libx11-6 from 
version 1.0.3-6 to 1.0.3-7. The rdesktop folks are working on a fix for 
rdesktop (the patches floating around the net seem to still have issues), but 
in the meantime I still need to use rdesktop, and the segmentation faults are 
getting annoying. 

I need to downgrade libx11-6 to version 1.0.3-6. I tried the following and it 
did not work:

1. Edited /etc/apt/preferences to look like this:

Package: libx11-6
Pin: version 1.0.3-6
Pin-Priority: 1001

Package: *
Pin release a=testing
Pin-Priority: 800

Package: *
Pin release a=stable
Pin-Priority: 600

2. I then did an apt-get update and apt-get upgrade. I thought this might 
downgrade the package, but it didn't.

3. I then tried apt-get install libx11-6=1.0.3-6 and got this error message:

Reading package lists... Done
Building dependency tree... Done
E: Version '1.0.3-6' for 'libx11-6' was not found

I searched the Debian site and could not find the older libx11-6 package for 
i386. Is there a repository somewhere with older versions of packages? My 
hunch is that I need to add an entry in my sources.list for a repository of 
the older version. Google did not come up with any obvious choices. 

Also, am I doing this whole package downgrade process correctly? Is there a 
better way?

Thanks!

Mark