please help to repair apt/aptitude

[Joydeep Bakshi <hizibizi@spymac.com>]

Hi debian users,

this is my very first mail at this list. I was a RH user but after knowing 
about debian I have changed my linux box to debian permanently. I really 
enjoy this disto. of linux as it comes with huge packages and some strong 
technical design. recently I have faced a very serious problem in debian. I 
have executed      *aptitude install lg-all*    and after that when ever I 
try to run aptitude to install or remove it says

Reading Package Lists... Done
Segmentation faulty Tree... 71%

I have also executed    *apt-get check* but it also provided exactly the same 
as above. now I am in a situation where I can't install or remove any 
packages from my system . could any one pleaseee help me to repair the 
aptitude ?  ( I have ran memtest and out put didn't show any error )

please CC to me.
thanks in advanced.