The instant suspect is conf/Bot.conf

Not that, unlike windows, *nix filenames are case sensitive so bot.conf is not the same file as Bot.conf. If the file is all lower case it will never be loaded.

Also check the file permissions.

I will look at adding fatal errors when config files are not found or cannot be loaded, but for now you'll just have to double check the files manually.
Never mind that. That file is required so it should be fatal if not found.

Need to do a bit more research.

But please do double check the username and password that is in conf/Bot.conf

Also please include distro, kernel, architecture and build version of PHP.

I run the bot from the directory it's installed in, and it's the only bot on this machine.

Here's the main load of information you are looking for...

Bebot 0.4.3 - installed
MySQL 5.0.51b

> php -v
PHP 5.2.4 (cli) (built: Aug 31 2007 23:57:08)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies

> php -m
[PHP Modules]
bcmath
bz2
calendar
ctype
curl
date
dbase
dom
exif
fbsql
filter
ftp
gd
gettext
hash
iconv
imap
json
ldap
libxml
mbstring
mcrypt
memcache
mhash
ming
mssql
mysql
mysqli
oci8
odbc
OpenBase Module
openssl
pcntl
pcre
pdf
PDO
pdo_mysql
PDO_OCI
pdo_pgsql
pdo_sqlite
pgsql
posix
Reflection
session
shmop
SimpleXML
snmp
soap
sockets
SPL
SQLite
standard
sysvmsg
sysvsem
sysvshm
tokenizer
wddx
xml
xmlreader
xmlrpc
xmlwriter
xsl
zip
zlib

[Zend Modules]

> Starting the bot gives...

_/_/_/      _/_/_/  _/_/_/      _/_/        _/_/   

         An Anarchy Online Chat Automaton         

             v.0.4.3 - PHP 5.2.4     

===================================================

Connected to MySQL

Botname [2008-06-26 03:36:46]  [CORE]  [LOAD]  Security.php
Botname [2008-06-26 03:36:46]  [SETTINGS]      [LOAD]  Loaded settings from database.
(all the otherstuff in between loads here cleanly)
Botname [2008-06-26 03:36:50]  [LOGIN] [STATUS]        Connecting
Botname [2008-06-26 03:36:51]  [LOGIN] [STATUS]        Authenticating
Botname [2008-06-26 03:37:15]  [LOGIN] [RESULT]        Error
Botname [2008-06-26 03:37:15]  [LOGIN] [STATUS]        Logging in
AOChat: not expecting login.

... then goes into startup loop, trying again.

Anything else you need?

Everything verified as per your request, here are the files...

As an update, this is a direct copy of my Windows bot, which works fine, the only difference being the clarification of the PHP binary in StartBot.php

Windows runs, I stop it, *nix version fails, and I can restart the Windows one again no problem.

I don't profess to being a *nix person, but followed the guidelines as per all documentation. Frustrating, but I'm sure you gods can sort it out

One thing that got me when I used a linux system was the username is case sensitive. That might be another place to look.

Just do a simple output of what the variable is that is being sent, should be pretty easy to see it.

Well I put my username and password in bot.conf and mysql.conf and it connected as it should.

What may be an issue is character encoding if you use some special characters. Try removing the lines in the conf files and type them up from scratch.

It may (in theory) be that your php and bcmath is broken. If that is the case re-building php and bcmath from source is an option.

Which distribution are you working with?

Edit: Have you tried all lower-case username?
Edit: When I pourpously enter the wrong username I get the error message you got.

Which architecture is the bot running on? It could be caused by 64-bit intigers not overflowing like 32-bit ones. (ie. they will not).