Looks like commenting "--enable-experimental" corrects my core issue.
What about making it optionnal ?

Using something like:
--- Makefile.orig       2007-02-22 23:23:18.000000000 +0100
+++ Makefile    2007-02-27 15:11:50.000000000 +0100
@@ -25,5 +25,4 @@
 CONFIGURE_ARGS+=       --with-tcpwrappers
 CONFIGURE_ARGS+=       --with-zlib=${BUILDLINK_PREFIX.zlib}
-CONFIGURE_ARGS+=      --enable-experimental
 CONFIGURE_ARGS+=       --enable-readdir_r

@@ -55,9 +54,13 @@

 PKG_OPTIONS_VAR=       PKG_OPTIONS.clamav
-PKG_SUPPORTED_OPTIONS= curl milter
+PKG_SUPPORTED_OPTIONS= curl milter experimental
 PKG_SUGGESTED_OPTIONS= curl

 .include "../../mk/bsd.options.mk"

+.if !empty(PKG_OPTIONS:Mexperimental)
+CONFIGURE_ARGS+=       --enable-experimental
+.endif
+
 .if !empty(PKG_OPTIONS:Mmilter)
 # force use of pkgsrc version of libmilter -- clamav uses the sendmail
binary


>>
>> Hello,
>>> I upgrade my mail/clamav installation to 0.9 (on NetBSD
>>> 4.0_BETA/sparc64) and the clamscan seems to core very often.
>> I had similar issues on sparc Solaris10.
>> In my case it happens when scaning excel files with clamav 0.90.
>>
>
> I could grab 3 cases of core and they were emails with .doc attached.
>
>> Either comment out --enable-experimental or look at bug #329 at
>> https://wwws.clamav.net/bugzilla/show_bug.cgi?id=329
>
> I'm gonna try to comment the experimental option.
>
> Thanks,
>      Jo