>IMHO: this is unnatural to a native speaker.  (I don't know where Mike got his
>rule from, although it may be correct for 99.99% of cases in his locale.)  The
>passage should read: "...lack of progress means they are
not...".  It could be
>countable, in either the case of there being many (persons) involved, or in the
>singular case of one person, when speaking of 'their'.  English can be
>annoyingly imprecise at times.  8-)

That is how I would also say it, as lack is singular.  :)

Mike

---
 þ SLMR 2.1a þ My wife made me join a bridge club...I jump next week.