Photoshop CS3 Killing RAM on closed files

Hello,

I'm having a bit of a problem with CS3 photoshop on Mac OSX,
the problem is this:

After opening a file and working on it, i click save and close the file. When i open the next file, the memory active from the last file is still open. After working on a few files suddenly it takes 20 minutes to save a relatively small picture file.

Initially i thought maybe it was because i may have bridge open along with photoshop and bridge is making all the picture previews, so i opened the activity monitor, and watched what happened when i opened and closed applications and files.

start out nothing open: active memory is as low as it gets.
open bridge: bridge uses something like 100 MB for all the RAW photo previews etc.
open photoshop: standard with nothing open it's about 80 MB
open picture file: work RAM usage in photoshop goes to something like 120MB add a few layers etc. etc. Usage is up into the 300MB range
save and close file: photoshop RAM usage stays at 300MB
open a new file: RAM in photoshop goes up to 600 MB
this happens with each file i open and close until photoshop uses all of the available memory, after 3 or 4 files i have to force quite photoshop.

I thought maybe this was a MAC Problem, but i found a Vista user with the same issue, (He blamed Bill G) nothing listed from any of the Windows ppl seemed like it was a solution for me.

Anyone know anything about this?