The HAM-ISI BLEND_SWITCH_ALL screen wasn't working properly at LHO: it was impossible to switch all the blends at once (white screen).
This issue has been fixed by the Stanford crew (see Hugo's SEI log: https://alog.ligo-la.caltech.edu/SEI/index.php?callRep=391)
I've 'svn up' and everything works fine now.