After attempting to install the recent set of updates for 10.1, YOU
refuses to install updates which I skipped the first time, although it
does recognise them as being present. I skipped them first time because
I didn't have the .patch.rpms, and there are only .delta.rpms for
delta-ing from the install media, but not from the previous updated
version (packages mono-*2.10, MozillaFirefox-translations).

After downloading the .patch.rpms, YOU suggests to install the still missing updates, I click accept, YOU uses 100% CPU for a little while, then does nothing before offering to click finish. Clicking finish and restarting YOU produces the same result. zmd is disabled. Update source is ftp://localhost/, .patch.rpm are present and YOU doesn't complain about any files it can't find.

YOU has got itself into a state where it doesn't install a bunch of security fixes. Without manual intervenion on the command line this isn't fixable. Does 10.2b2 show the same behaviour??

The problem has to do with the blurbs created by yast in
/var/lib/zypp/db/patches/ These are yast's memory of what's installed
and what isn't. Unfortuately, 2 things happen:

1) Yast marks package-sets as installed even though some rpm part or all
of it was skipped, and also if yast was terminated forcefully after
selecting the whole lot of available patches.

2) Yast never checks its "memory" against reality, and forever after,
all of the existing patches so far are "installed".

Fix for now:  rm /var/lib/zypp/db/patches/*

Running YOU again now causes the missing rpms in the mono-* and MozillaFirefox patch set to be installed. YOU has now also forgotten any other patch previously installed, but that's cosmetic in comparison with being unable to install patches with YOU.

The the rpms were in fact not installed was checked with rpm -qa --last and rpm -q mono-data etc. It's not just a question of YOU displaying incorrect information.