You have setup mod_rewrite module in apache. When a URL is rewritten with the mod_rewrite Dispatcher does not process the rewritten URL but requests the original URL.
There is 2 possible scenario
1) Make sure you set the DispatcherUseProcessedURL to 1 (This tells Dispatcher to use the pre processed URL)
2) Add the passthrough flag [PT] in your apache rewrite rule. This will allow apache to pass the rewritten URL to CQ dispatcher. An example as follows:
In httpd.conf change
RewriteRule ^(.+)\.html(.*)$ $1.reg.%1.html$2
RewriteRule ^(.+)\.html(.*)$ $1.reg.%1.html$2 [PT]