Have you tried running either Birdie and VisualPrefs without one of the others? VisualPrefs and Birdie both put a line in the startup-sequence.
Are you sure that the problems are caused by Birdie? Try doing what I always do, when the machine isn't booting as it should...
Split the startup-sequence into 5 parts. By splitting it I mean put an echo command in different places of the startup-sequence. When the Workbench loads, it will write the string in the echo command, so you can see what has been completed, and were the error occurs. When you know in which part the error occurs, split this section up into small parts, until you know at which line the reset kicks in.
As you seem pretty sure that it's Birdie that is giving you the troubles, try editing your startup-sequence and put this in
echo "Loading Birdie"
Birdie bla bla bla
echo "Done loading Birdie"
Have you tried checking for viruses? Cured my highly unstable system back when I was upgrading from Blizzard 1230 to Blizzard 1260.
