Have a small OSX network consisting of a Mac Mini server (Mid 2010 4GB RAM 2-500 GB HD) and 20 27 inch iMac client workstations used by around 350 user accounts. All were originally running Snow Leopard for over 2 years and did fine. Decided to do an in-place upgrade to Maverick on Server and workstations a few months ago. Immediately had an issue with the network users icons not displaying correctly on the client workstations. I would see the first 25 icons fine but the rest were not visible. I know they were there as the left/right arrow buttons would let you scroll to the end and back but the icons past the initial 25 were not visible. If you were to pause in the area of blank icons and wait 15 minutes or so the icons would appear on the screen, but it was only "their group of 25 or so". If you then scroll past these the icons to the left or right the other (including the first 25) were still not visible!! Also need to mention that logon was incredibly slow...like 3 minutes or more. After a couple of weeks the problem went away. I assumed a patch had resolved the issue or things just "settled down". Worked fine since. Began to experience other issues and decided to do a fresh install of Maverick 10.9.3 on the mac mini server this week. The icon visibility issue has returned!!! What could be the problem? I think DNS is fine as it checks out correctly and worked fine with Snow Leopard. I use profile manager on Maverick and it works and responds to the client workstation promptly and correctly. All clients and server are on a single 24 port Cisco switch. Internet bandwidth is ok but not extreme. I have bound (and unbound and rebound) the clients to Open Directory and this seems to work as they resolve the DNS name correctly. Any ideas on what could cause the network user icons to not display correctly on the clients? Or would cause the logon (both network or local account) to be so incredibly slow?? I am out of places to look.