Hmmm openacs-5-6-6-final is the latest release of openacs. I am not sure what version of xowiki works with that version of openacs.
No version of HEAD is really considered stable until it is branched to a release branch.
If you encountered errors upgrading from a 5.5 release to 5.6 release we can probably help and that would indicate a bug.
If you upgraded from a HEAD checkout and attempted to upgrade to another HEAD checkout, it will be difficult to determine exactly what the problem is, but if you want to post what errors you noticed, we might be able to help.
Upgrades from unreleased code is difficult to support and generally only upgrade from beta to final releases is supported.
It would be impossible to test every possible combination of checkout from HEAD for upgradability.
