The AZ11 was never a very reliable motherboard from the beginning, as were many other earlier Athlon boards from other manufacturers as well, including Asus. I've dealt with the AZ11E a couple times and that board is stable, I haven't come across any troubles yet. I've put together three computers built off of the AD11 board and all three perform without any problems. The biggest difference going to the AD11 board is using AMD's chipset. With the reports that appear every so often around the net about troubles with VIA, it's going to take a while before I ever consider buying a board with their chipset again.
I was having problems early on with my new upgrade, my system would lock up constantly. I replaced out my video card's heatsink and fan for a better one and put heatsinks in the video ram chips, I run an MSI Geforce2 GTS Pro card. I also put on Termaltake's memory coolers onto my system ram chip. Ever since then my computer has been solid, never a lock up, and I'm running games at 1280x1024x16 no problem.