Truncated file in GPG?

[Charles <test524@comcast.net>]

Hello all,

I'm running GPG version 1.0.6 on Debian stable for the first time. 
Kernel version is 2.4.18. I'm trying to perform a relatively simple 
task: encrypt a big MS Outlook mail archive file so that only I can 
decrypt it. I created a key for myself, and encrypted the file with

gpg -e -r Charles mail.pst

mail.pst is a 116MB file.

The resulting mail.pst.gpg is 80MB. Something is clearly wrong. Though 
I'm aware GPG has compression, PST is already a pretty compressed 
format. Doing gpg -d to decrypt gave me back a file that was about 81MB 
-- far smaller than the original.

charles@compute1:/files/Work$ gpg -e -r Charles mail.pst
charles@compute1:/files/Work$ ls -l
total 200208
-r--------    1 charles  charles  122470400 May  2 22:11 mail.pst
-rw-r--r--    1 charles  charles  82329455 Jun 18 21:41 mail.pst.gpg

What's going on here? I'm running on a 667MHz P3 with 128MB RAM.

Any help most appreciated.

Thanks,

Charles.