I can confirm the problem as it still happens to me occasionally. In my case at least, it's caused by a very, very slow connection and any actions I take to scroll or otherwise view a new part of the screen. In particular, if I click on a thread (especially the <<all>> tag in the page list) and then fail to wait for all the content to arrive at my computer, I will get black rectangles (unrendered content) and out of order content if I scroll down. I've learned to wait until the status line at the bottom of Firefox no longer displays "waiting for elliquiy.com", "transferring data", or anything indicating the complete page has not arrived yet.
This may be a problem with other browsers as well but since I only use Firefox I can't confirm that.
An aside - I hate waiting but I have exactly one ISP choice out here in the sticks and they have a "We have your money and don't give a damn." attitude.
A satellite ISP is out of the question as I would use the entire monthly bandwidth allowance in less than two days.