Strange bug with PHP on Windows 7

This is the configuration: Windows 7 Home Premium, XAMPP 1.7.3 (Apac开发者_JAVA百科he 2.2.14 , PHP 5.3.1), Firefox 3.6

This is the PHP-code in a file named 'test.php' in htdocs:

<?php echo('04556-8978765'); ?>

On http://localhost/test.php I would expect to see the string 04556-8978765 in the browser. This is not what happens, though. The string appears for a short time and then it disappears altogether. Firebug shows an empty body-tag. However, when I look at page source, the string is there alright.

When I change the string in the echo-statement to e.g. 4556-8978765, everything is fine.

Internet Explorer 8 does not show this strange behavior.

I could not reproduce this with the same Apache/PHP/Firefox configuration on Windows XP.

'04556-8978765' is by no means unique. The couple '02065-96047' and '02065-9604' behave exactly the same.

Can anybody reproduce this and offer an explanation as to what is going on?

PS: If you can not see the string '04556-8978765' in the echo-statement above, look at this post with IE8.

If IE8 doesn't show the behaviour, then it's unlikely to be a bug with the PHP/Apache server. Try starting Firefox in "safe mode", with all extensions disabled, and load the page. Perhaps it's related to Firebug or another extension?

Also try with some other browsers like Opera or Chrome if you have access to them.

Problem solved! It wasn't ad blocking software as suggested by Col. Shrapnel but the Skype extension I had installed. Everything is fine now that I have it removed.