Segmentation faulty Tree - aptitude

[jb701@uku.co.uk]

I was seeing if a memoery stick I had was any good, and put it in my debian 
machine.  All seemed OK, so I tried to install memtest. 

Went OK until I got aptitude existing with a segmentation fault.  I 
rebooted, but I still get a segmentation fault. I tried to reinstall 
aptitude with apt-get [maybe that doesn't make sense!] and I get the 
message: 

Segmentation faulty Tree 50% 

as it tries to build up its tree. 

Can I save this installation or am I going to have to reinstall? 

I have removed the suspect RAM of course. 

- Joe