I faced some problems with CMS Made Simple version <=1.2.3 - my browser (usually Firefox) tried to download index.php instead of showing the real content. This problem occured quite often, but not on every page load. And usually while using Album-module. I checked out headers web server was sending (with Firefox Live HTTP headers plugin) and noticed that Album-module was not sending Content-type for the image or page. And all content was compressed.
So my educated guess was that browser couldn't decide what to do with this content and opened download-dialog. Then I noticed that my web server had zlib compression turned on. I turned it off, and everything worked just fine after that.
So, if you have this kind of problems, add .htaccess to your CMSms root directory and add line:
php_flag zlib.output_compression Off
Or edit your php.ini / virtualhost/httpd.conf directly.
Hope this helps someone
