portupgrade -af on FreeBSD 5.3 and I get two conftest signal 12 core dumps ?!!

I've recently migrated to FreeBSD 5.3. I just upgraded my system to the 
brand new 5.3-RELEASE version, and first of all, I have to tell you that it 
works really great!! I love it! Thank you guys for the great work!!

But I run into a somewhat weird problem. After the successful migration to 
5.3-RELEASE from a previos 5.2-CURRENT version, when I recompile all 
installed ports with 'portupgrade -af', I get this in my system log file:

Nov  6 16:59:54 www kernel: pid 8927 (conftest), uid 0: exited on signal 12 
(core dumped)
Nov  6 17:14:16 www kernel: pid 2733 (conftest), uid 0: exited on signal 12 
(core dumped)

But portupgrade proceeds and seemingly re-compiles all installed ports 
anyway (at least this is what I believe). When I look for the .core file(s), 
I can't find any on my hard drive anywhere! If the core was really dumped, 
then where did the .core files go? And how can I find out which port(s) are 
causing these problems? What is this signal 12 with conftest means anyway? I 
couldn't find anything about it by Googling...

Other then this, my system works great with FreeBSD 5.3! And it has never 
been this smooth and fast before!

And one more question. When I cvsupped all-src for FreeBSD 5.3-RELEASE, I 
used the RELENG_5_3 branch. Or should I have used RELENG_5_3_0 ? What is the 
difference between the two now, as FreeBSD 5.3-RELEASE was just released 
this afternoon? I guess, nothing. Am I correct? Or should I cvsup 
RELENG_5_3_0 ? Please advice!

Zoltan