2Doug Bissett: You are wrong. OS/2 version of VBox 1.6.x never supported VT-x/AMD-V. (because of missing features in OS/2 kernel). It only worked on other platforms. And, Readme mentions that VMX is not supported, so you must know if you have read readme.
Hmmm. There isn't much of a README, but it seems that you are right. My Warp4 guest has Virtual Machine Assist enabled, and it does boot, at least up to the boot logo, then it seems to hang.
My WinXP guest also has that enabled, and it seems to work fine (don't know if it actually uses that stuff).
More work to do, when I find the time...
It could also be the case that the non-YUM/RPM SDL install (the previous releases, last of which in my machine came from the SDL-1.2.15-20160209.zip file) is somehow causing ANPM/YUM/RPM a problem.
If you have installed ANPM (YUM) managed packages in any other way, at any time in the past, you really should install them using ANPM (you may need to ignore a warning message that they are already installed, but be sure to reboot if that happens), and eliminate whatever was installed previously. If you don't do that, you can have problems. Whether that is what caused your current problem, or not, I can't say. I do know that RPM packages can be, and have been, built incorrectly, and that causes problems for ANPM (and YUM from the command line). In this case, it appears that the ffmpeg package (and possibly others) are calling for sdl, which happens to exist, for some reason, so it gets installed. Later, SDL was released, but it is not recognized as being an update to sdl, so it doesn't get updated.
As I have said before, RPM/YUM is a terrible way to do things, but if you want to use modern software, you need to use it. ANPM is simply a front end processor that runs YUM for you, but it can't detect, or correct, every problem that bad packages create.
It seems that once you get the sdl package uninstalled, and the SDL package installed, you should have no more problems with that (until they screw it up again).