Apple II (rev1) instability...HELP!

[Nama <forums6000@mac.com>]

Hi all,
Me again.
I've recently sold one of my Apple II, and I am moving all my cards
over to another rev1 Apple II that I own.

I'm trying to find out why this system works fine 90% of the time,
while the other 10% it crashes and hangs or just displays odd
behavior.

Setup is as follows and is identical to my previous machine:

0 - Ram card
1 - CFFA #2 ( (prodos 1.1.1 / contiki))
2 - SSC
3 - empty
4 - Uthernet
5 - Echo 2
6 - Floppy I/O
7 - CFFA #1 (turnkey startup to DOSmaster 1.7)

Of course I have tried the system with minimal cards and it still
exhibits weirdness.

Symptoms:
-Sometimes hangs on boot.
-Strange inverted period often seen in top left corner when booting
from CFFA #1
-Sometimes craches to the monitor
-Doing a IN#1 to launch the CFFA #2 always hangs with a strange
flashing inverted period in the top left corner. often with corrupted
type on the prodos launch screen.
-Once it up and running it's usually fairly stable unless I reboot.
-Have run a looping game for many hours with no problem, but crashed
to monitor as soon as I restart.

What I have done:
Tried a new set of ROMs
Run Apple test utils on the RAM and ROM...no problems found.
Run the machine from a known good IIe power supply.

If anyone here can shed some light on my problems, I would be very
grateful. I'm hoping the inverted period may be a good clue to whats
happening.

I've uploaded some bad photos here if this helps at all:

http://web.me.com/lord_philip/apple_1_%26_II/rev1.html

Much thanks in advance.

Phil