install fails with http 500 error

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04 Nov 2011 03:09 #2099 by WWWebsites
joomlamailer version: 1.7.2
Joomla! version:1.5.21 stable
PHP version:5.2.17
MySQL version:

I have installed on several of my websites your awesome component and one already today but this one will not even take the install. from the install page in joomla I selected the downloaded zip of the main component and clicked upload file and install. it thought about it for a minute and then goes to a screen "website can not display the page HTTP 500"
Is this because this is an old version of Joomla? Or is it one of the other components I have installed (Events Booking, Projoom install, and Projoom's Smart Flash Header)? or something else? Please help :)
In gratitude
Michelle

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