SCO Unix OSR5.06 box doesn't bott anymore

Hi,

SCO Unix OSR5.06 + 5.06a supplement.
SuperMicro motherboard, bi-PIII Xeon 700
1Gb ECC ram
Icp vortex GDT7523RN SCSI raid controler
external hdd array with 5 + 1 hdd in raid-5
hdd's in channel-A scsi
tape drive SLR60 in channel-B scsi,

this server is running since 1994 without any problem.
this morning, a kernel trap was happend.
I had many difficulties to boot it, sometimes it worked, sometimes not
(the system freeze and/or kernel trap happend)

I could make a backup of /root with Lone-Tar utility.
the /u file system was backuped saturday.

Now when boot up, the system freeze at

%cpu ...
%cpuid ...
%fpu ...

So what's next step ?
What's wrong ?
Could it be some corrupted /dev/swap ?
(because after some kernel trap, the system said at boot time that it
could not identify if there is something or not in then /dev/swap
device, or : bad adress message).

Should the restore of / filesystem via Air-Bag utility resolve the boot
problem ?

Thank's.

F. STOCK