SYS/OS:
Linux openSUSE-103-64-LAMP 2.6.22.13-0.3-default #1 SMP 2007/11/19 15:02:58 UTC x86_64 x86_64 x86_64 GNU/Linux

=== CUT ===
Build: POL097-2008-02-26 Coregina (gentoo)
Last Script: pkg/packetHooks/BFCommand/unknownOne.ecl PC: 1
Stack Backtrace:
[0x8220ea0]
[0xffffe500]
[0x81690dd]
[0x80743dc]
[0x807512e]
[0x815819a]
[0x815a595]
[0x815ad7e]
[0x8163a1a]
[0x80f95c5]
[0x80f9ce9]
[0x8229088]
[0x8284e21]
[0x8048151]
=== CUT ===

Content of unknownOne.src:

program unknownOne()
return 1;
endprogram

exported function HandleUnknownOne( character, byref packet )
// These 2 lines are used to fix unused var reports during compile.
character := character;
packet := packet;

// No need for core to see this packet, block it.
return 1;
endfunction

It's unlikely to be unknownOne.ecl causing the problem. The packethook is the same on my shard.

Does it crash every time you start? What else have you changed?
Do you have more than 1 packethook handling the BF packet?

Does the error appear just when it is printing all the installation of the packethooks? What's the next hook it tries to load?

Does pol.cfg have these options set?:
LogLevel=20
DebugLevel=6

They might give more information.