There are some versions of Xdebug that are not completely compatible with their PHP counterparts. You might want to try an older version of Xdebug from Xdebug.org:
http://xdebug.org/download.php

Also, running the "php -m -c path_to_config.ini" may give some indicators on what is happening.

Cheers,
Todd

Recently I acquired the Komodo IDE 5.2.4, build 37659, platform win32-x86. I installed it in a computer with Windows Vista. In this computer, I had and older version of Komodo (Komodo 3 personal) and I am using XAMPP from Apache Friends. The version I have in this computer of Apache Friends its the 1.7.0 released on January 2009. In this case Komodo IDE 5.0 recognized correctly PHP for debugging. PHP version in this distribution is the 5.2.8.

However, latter I tried to install the Komodo 5 in a Server running Windows XP. This time I tried to install the latest version of XAMPP which is the 1.7.3 and includes PHP 5.3.1. The same cited message appeared when using the wizard to configure PHP debugging:

Sorry PHP debugging configuration failed. PHP is configured but is unable to load the debugger extension at C:\wamp\bin\php\php5.3.1\ext\php_xedebug.dll.

The xdebug extension was found for PHP but couldn't be loaded - build info for C:\xamp\php\php.exe:

Platform Windows
Version 5.3.1
debugBuild:0
compiler:MSVC6
threadsafety:1
architecture:x86

I checked in xdebug.org and tried to install older versions of xdebug, but they didn't work. Also I checked the xdebug versions at http://aspn.activestate.com/ASPN/Downloads/Komodo/RemoteDebugging
but I had also the same error.
Something similar happened to me with Komodo 3.5 some time ago, but I was able to resolve it by replacing the xdebug.
Finally I tried to install PHP directly, replacing the php version included in XAMPP. PHP version was 5.3.1 released on Nov 19, 2009. I had same the message with Komodo, and an incompatibility message from php, indicating that php is using a newer zend xdebug version and an error with bz2.

The command php -m -c path_to_config.ini

Shows:

[PHP Modules]
bcmath
calendar
com_dotnet
ctype
date
dom
filter
ftp
hash
iconv
json
libxml
odbc
pcre
Reflection
session
SimpleXML
SPL
standard
tokenizer
wddx
xml
xmlreader
xmlwriter
zlib

[Zend Modules]

I've seen a few issues with this over the last couple of weeks relating to recent XAMPP and MAMP versions with PHP 5.3. In most of these cases (still working on one), it's been solved by replacing php_xdebug.dll with a 2.0.5 Xdebug binary from here:

http://xdebug.org/download.php

With your build of PHP, the one you want is:

http://xdebug.org/files/php_xdebug-2.1.0beta3-5.3-vc6.dll

Put this dll somewhere other than your current PHP /ext/ directory, and remove this copy from your current installation:

C:\wamp\bin\php\php5.3.1\ext\php_xedebug.dll

Make sure the Xdebug section in php.ini points to php_xdebug-2.0.5-5.3-vc6.dll, then try `php -m -c path_to_config.ini` again.

[Edit: Changed link from Xdebug 2.0.5 to 2.1 to avoid this bug.]

With xampp 1.7.3:

php_xdebug-2.1beta3-5.3-vc6.dll
from the xdebug site worked for me