[TYPO3-english] calendar extension 500 error in cloud

[listas at tu3w.net]

Hi folks,
Recently we're using the Rackspacecloud infrastructure to host some  
Typo3 websites.

Today as we wanted to install the calendar extension (version 1.2.0  
/Typo3 version is 4.2.8) we got a 500 error, as follows:

http://www.cce.org.ec/working/error500-uploading-ext-cal-typo3-cce-org-ec.gif

We've checked the permissions (set to 755) and the owner, however for  
some reason we still cannot get this extension to work. Other  
extensions like tt_news are installed correctly.

Some weeks ago, we installed the cal extension into another domain at  
the cloud without any issues.

.htaccess file is also the same in both domains:

php_value upload_max_filesize 10M
AddDefaultCharset Off

At the error log, there is nothing about this.

Any ideas what else may we look at?

Thanks in advance for your support.

Best regards from Quito,
Miguel