Ok, so here are the results of my tests. With 3.0BETA updated on 04/19, the
computer still crashes. On the other hand, with -current as of 04/18, it works
perfectly.

Maybe a relevant fix added to -current had not yet been transfered, as 
of 04/19,
to 3.0BETA? Do you know if it was pulled up now? I would love to use 3.0BETA
rather than -current for this server, but frankly I don't want to risk another
server crash too soon... (it is a half-production server with lots of 
important
information stored on the disks)

Anyway, I am glad it's stable now. Thanks all the help!
Marcello

>> > No, this won't work. It should have picked sys/arch/x86/include/intrdefs.h
>> > by itself. Are you sure your source and build directories are clean ?
>>
>> Well, good news is that the computer didn't crash last night with the latest
>> 3.99.3. Since I didn't feel like risking a disk crash, this time I let both
>> Dom0 and DomU idle, but I bet it didn't influence the result. Tonight I'll
>> load DomU again, anyway.
>>
>> Bad news is that I still can't get netbsd-3 to compile. To be on the safe
>> side, I deleted /usr/src and checked out netbsd-3 from scratch. I didn't get
>> the same errors as yesterday, but I still had an error (BTW, I am compiling
>> the kernel on DomU -- I hope this is not a problem). Here is the sequence of
>> commands and the error. I used the stock XENU file.
>>
>> % cd /usr/
>> % rm -fR src
>> % cvs -z 9 -d anoncvs@anoncvs.netbsd.org:/cvsroot checkout -r 
>> netbsd-3 src/sys
>> [...]
>> % cd /usr/src/sys/arch/i386/conf/
>> % config XENU
>> % cd ../compile/XENU/
>> % make depend
>> [...]
>> % make
>> [...]
>> #      link  XENU/netbsd
>> ld -T ../../../../arch/i386/conf/kern.ldscript -Ttext c0100000 -e 
>> start -X -o
>> netbsd ${SYSTEM_OBJ} ${EXTRA_OBJ} vers.o
>> vfs_init.o(.text+0x22e): In function `vfsinit':
>> /usr/src/sys/arch/i386/compile/XENU/../../../../kern/vfs_init.c:359: 
>> undefined
>> reference to `vfs_list_initial'
>> vfs_init.o(.text+0x246):/usr/src/sys/arch/i386/compile/XENU/../../../../kern/vfs_init.c:360:
>> undefined reference to `vfs_list_initial'
>> vfs_init.o(.text+0x25a):/usr/src/sys/arch/i386/compile/XENU/../../../../kern/vfs_init.c:359:
>> undefined reference to `vfs_list_initial'
>> vfs_init.o(.text+0x26a):/usr/src/sys/arch/i386/compile/XENU/../../../../kern/vfs_init.c:361:
>> undefined reference to `vfs_list_initial'
>> *** Error code 1
>>
>> Stop.
>> make: stopped in /usr/src/sys/arch/i386/compile/XENU
>
> vfs_list_initial should be in  /usr/src/sys/arch/i386/compile/XENU/ioconf.c,
> generated by config(8). My guess is that your config binary isn't in sync
> with the sources.
>
> --
> Manuel Bouyer <bouyer@antioche.eu.org>
>      NetBSD: 26 ans d'experience feront toujours la difference
> --
>