regular expressions with upper case totally broken in gawk 3.1.1

[Tom Stockfisch]

Ever since linux WS 3.0 (gawk 3.1.1) my awk programs have been 
mis-behaving.
It seems expressions with upper case letters are all messed up.

Consider the simple one-liner:

        awk '/[A-Z]/ {print}'

This matches the input

        A

and also

        b

but not
        a

It seems as though all lower case letters except "a" are considered upper 
case!

If I set IGNORECASE=0 in a BEGIN section  I get the same result.