Admin-Customers opening for ages

Hey guys, wonderfull work all arround

here's my somewhat weird issue.
I'm running a store with some 7500 customers and have a very weird problem.
The whole admin works fine with the exception of Admin Customers. When I want to check some customers details and check Customers the queries take for ages - the last time I checked (just now) it took 8 minutes to open the customers screen, and when I try to find a specific customers it takes even longer.

On the other hand when I open any other admin subpage there are no problems, including orders with some 7K entries

I've tried optimizing, repairing tables in mySQL and in the shop, to no awail whatsoever.

I've had this problem since ZenCart 1.2.4, when updated to 1.3.0 it didn't hellp at all, now on 1.3.7 the problem is still here

Does anybody have or has had any similar problems, and any ideas how to fix this?

thx

server info:
** Server OS: ** Linux 2.6.9-023stab043.1-enterprise ** Database: ** MySQL 4.1.21-standard
** PHP Version: ** 4.4.4 (Zend: 1.3.0)
** HTTP Server: ** Apache/1.3.36 (Unix) mod_auth_passthrough/1.8 mod_log_bytes/1.2 mod_bwlimited/1.4 PHP/4.4.4 FrontPage/5.0.2.2635.SR1.2 mod_ssl/2.8.27 OpenSSL/0.9.7f

Have you done any "code customization" to the admin that may be causing it? What 3rd Party Admin mods are installed that involve customers? (Super Orders etc..)

My first thought would be to optimize your db etc..., but you say you have already done that. Do you ever notice (or get customer feedback) on whether your site runs slow at times as well? (that would point to a server php / MySQL optimization issue) more than likely as it would be occuring randomly on the site as well.

the only admin mod is super orders (as much as customers are involved) and I didn't have it installed when I first noticed this.

I've had some issues with site loading slowly, but according to the ISP they were server load related (no probs since I was moved to a new machine)

and woudn't that affect the whole site, not only Customers sections? as said, there are almost as many orders as customers, but admin-orders load almost instantly, and there are a lot more querries involved (i think)

thanks

I am looking at a client's site with 50,000 customers and the page took about 1-2 seconds ...

Perhaps you are missing indexes or have some other issues happening ...

How many do you display on each page?

I'm displaying 20 cust per page
indexes on main table zen_cusotmers and zen_customers_info , _basket , _wishlist etc all seem to be fine (am checking with default 1.3.7 tables now)

can somebody tel me all the admin files related to admin-customers page as am thinging of simply overwriting them with default 1.3.7 files

thanx for all the help

Could this problem be related to indexes in mysql!?