I just installed TF on a new machine, which has a Pentium D dual core chip, 3 GB of RAM, and a new Nvidia 7600 GS video card with the latest drivers. TF doesn't seem to download tiles at all, or a new tile will pop up every minute or so. This happens at all zoom levels and with all tile sets. Also, if I try to resize the TF window, it takes a couple of seconds to redraw on the screen.
Also, the screen resolution is 1920x1200. I was previously having the same garbling issue as in another post, but that was before I installed the new video card.
I'm using version 2.85 of TF.