Just a second ago the GSS/KB team republished the KB article that explain the vSphere 5.0 problem around SvMotion / vDS / HA. I wrote about this problem various times and would like to refer to that for more details. What I want to point out here though is that the KB article now has a script attached which will help preventing problems until a full fixed is released. This script is basically the script that William Lam wrote, but it has been fully tested and vetted by VMware. For those running vSphere 5.0 and using SvMotion on VMs attached to distributed switches I urge you to use the script. I expect that the PowerCLI version will also be attached soon.