Hi guys, just wanted to provide some input with the same issue that I've been dealing with for a couple weeks. It most likely is not your cable that is freezing the EVO.
When I first beta-tested the FullHDMI when it first became available, with a BestBuy Dynex cable, worked very well on my 32' Westinghouse LCD. I return the cable after a few days of testing, getting an adapter and full cable online, as the Dynex was 6 foot and not enough. This was with MikFroyo 4.5 I believe, and made a nandroid backup.
A few weeks later, I'm ready to start testing again. I start doing my research and see that there is another method, and as I prefer AOSP (CM7 Nightlies) I tried it out. The phone has since always frozen on my Westinghouse, but NOT on my roommate's 50' plasma. I have tried a multitude of kernels (stock, HDMI-accelerated ones), ROMs (many CM nightlies, Warm RLS 5, Fresh, and a couple more), with both mirroring solutions, and also stock Sense functionality. I even tried the Dynex cable that previously worked on my Westinghouse, with my old nandroid, and it still freezes.
Through my research I've read that it's an EDID parsing error in the kernel, but I don't understand why older sense ROMs with stock kernels are freezing now. My old MikFroyo nandroid worked great before I ventured into any other solutions...