The X servers are not 64-bit clean. If you attempt to open more than 25-30 windows, the X server will crash. This is so serious a problem, as I don't think Red Hat should ship an Alpha version until it is fixed.
We update X as frequently as possible, using XFree86 sources, which are based on The Open Group's reference release. They are working very hard on making everything 64 bit clean. However, X is far from useless at this point on platforms such as Alpha and UltraSparc. 25-30 windows is usually the exception rather than the rule.