Flickr recently replaced one of their library functions:
getElementsByClass(classname,tagname)
with
Y.U.Dom.getElementsByClassName(classname,tagname)
So a number of GreaseMonkey scripts that used the old js library call are now broken. The scripts ive found to be affected so far are:
group pool: warn + delete, flickrpm, groups organiser, contacts organiser, flickr quoter and flickr shades. Quas's group tracker script is also affected.
You can get updated versions of the above scripts here: http://steeev.freehostia.com/flickr/.
You can also read more about it in the flickr hacks group here