That was my hunch too -- the last time I saw anything like that, it was in Titan Quest, years ago. My husband said it was a texture memory problem, as in, my video card memory wasn't handling the huge influxes of textures every time I'd teleport, so I'd get black/blank textures. Well that was no surprise to me, as that video card was old and I'd really beaten the crap out of it, and it died a few weeks later.
But generally the subset of people who use EC have good to decent to bleeding-edge PCs -- we're technophiles! It surely can't be that you're ALL trying to make crap video cards stretch a few months longer, it just can't be. I have two nvidia 9800 GTs in SLI config (1gb video memory), which IS nice, but it's still only middle-of-the-road good for 2009. And this is an eyesore 2D game from 1997 for crying out loud. There's no excuse for it to be flaking on even crap video cards. You should not need what I have to play this client.
Grump grump grump. I feel for you guys.
Edit -- just in case anyone is mining this for data, I had a single 8800 GT (1gb memory) before this past week, and never had the problem then either. I DID see it in KR, however.