On Thursday, Citrix released a hotfix that resolved an issue where Virtual Machines would crash when migrated on Intel Nehalem processors. If you are using Intel Hardware with EPT support, you should install this hotfix.
You can download Hotfix XS55E002, CTX122348 at the link below.
http://support.citrix.com/article/CTX122348
Just an update on hotfix 2: we’ve rolled it up into hotfix 4, which fixes another EPT issue. You can download hotfix 4 from http://support.citrix.com/article/CTX122705.