The problem first appeared when GNU awk in 3.0-CURRENT was apgraded to
3.0.3. I run C-News, which uses awk extensively. After awk apgrade C-News
expire stopped to work. It appeared that some GNU awk 3.0.3 programms when
given absolutely legitimate input fail, giving out a number of messages:

awk in free(): warning: chunk is already free.

Fix: 

I was not able to track the error in awk sources. As a workaround,
I just reverted to GNU awk 2.15.5.
How-To-Repeat: 
Run the following awk program (it is cut out of C-News expire scripts).
I was not able to cut it down more -- omitting some portions of the
code (e.g. OFMT line), make error go away in this case, though it
certainly does not fix awk.

----------------cut-here----------------
#!/usr/bin/awk -f
BEGIN {
	OFMT = "%.12g"
	big = 99999999999
	lowest = big
	small = 0
	highest = small
}

$0 ~ /^[0-9]+$/ {
	if ($1 < lowest)
		lowest = $1
	if ($1 > highest)
		highest = $1
	next
}

$0 ~ /^[a-z]+/ {
	print dir, highest, lowest
	dir = $0
	lowest = big
	highest = small
}
----------------cut-here----------------

To get the error, just give this script the following input:
----------------cut-here----------------
a
1
b
----------------cut-here----------------