Zencart Admin Issue - Please Help!

Hello, I was able to use my admin for zencart with absolutely no prolems until about an hour ago. I can click on all the different areas in the admin and it works fine. But when I click on a product to edit it, it runs extemely slow and when it does load and I click on preview button, it doesn't work at all. I don't understand what's causing this problem because my site runs pretty good and the admin runs like it should except in those 2 areas. Does anyone have any solution to this problem? Any help would be appreciated!

Thanks Tara

trying to locate some other threads on this, but I too have this problem and only in admin, and only during random times.
Most of the time all is as it should be, but every once in a while the admin side only will bog down, then like "magic" disappears .
1st before you ask, I am the host,.. this is one of my dedicated servers, and only two site are installed , so I dont think its host related, now here is the odd part, while working in the store one day and trying to combat the lag in adding/editing items, as soon as the server hit midnight, the problem was gone.
running 1.3.7 with latest pach set
CPU is a 3.4 Ghz duo core
2 GB RAM
100Mbps connection
server load is under .5
does ZC do any housekeeping chores?
any thoughts, advice,?

AndyII:

does ZC do any housekeeping chores?

The only "housekeeping" that Zen Cart does is update product expiries on specials/sales/banners on the first visit after midnight, server-time.
There are no built-in cron jobs etc.

Occasional lag suggests database congestion or heavy CPU utilization.

well when I run off to putty and shell in, I see no problems, cpu loads are low, memory is sufficient, no other commands show problems, and like said, this particular server has only two ZC installs on it, dedicated to just these 2 stores, as they are digital download stores and need the HD space and bandwidth.....

- What kind of things "slow down" in the admin?
- Is there any pattern to the kinds of things you're doing when it happens?
- When it happens, if you open phpMyAdmin and click on Show Processes, are there any locked queries or queries pending execution while a database lock clears?
- do you have a shell tool to show you the currently-running queries, such as mytop?
- what version of Zen Cart?
- is this an upgrade? from which version?
- what addons/contributions are installed?
- how many products in the database?
- how many (average) attributes are connected to each product?
- how many visitors/customers are on your site at the time when the admin slowdowns seem to occur?
- do *both* your sites on this server have the same problems, at same time?
- how long to the slowdowns last before they clear up?