acer extensa 5630, btx loader panics (cd boot)

[Ilya Zhuravlev]

I'm trying to install 8.0-beta2 amd64 on this hardware:
core 2 duo T5800, 2GB, chipset mobile GM45 express, 160gb sata, wifi 
Atheros AR5007EG
vendor partnumber EX5630-582G16Mi

error:

BTX loader 1.00 BTX version is 1.02
Consoles: internal video/keyboard
panic: free: guard1 fail @0x7b397074 from 
/usr/src/sys/boot/loader/../../common/console.c:94
-->Press a key on the console for reboot<--

In bios I can change only "load default setting" and ATA-mode (AHCI/IDE) 
options, and applying any of them doesn't make any sense.
Googling doesn't get results for related errors.
It seems that console.c was not changed for the last 3 years, 7-releng 
was skipped and I've tried to boot with 6.0-release i386 (btx loader 
1.01) - succesfull.
What can I do?