If I am not mistaken r7555 is between 8.0.1.RC1 and RC2 and thus newer than 8.0.1-beta3 (I went through the larger size-change some releases before r7555).From the announcement:
You can't perform an in-place GUI upgrade to 8.0.1-RELEASE or 8.0.2-RELEASE from a release prior to 8.0.1-BETA3 - you must create a new install.
But it is a nightly and maybe something broke after RC1 and was fixed in RC2?