Performance Slow and error message!

Performance is very slow with my site.  It sometimes takes well over 1 minute to load a page and my site is not being used by the public.  I've set up a cron job to ping the "KeepAlive" every 5 minutes.

When the site really chugs I get the following error:

Item has already been added. Key in dictionary: 'RegEx'  Key being added: 'RegEx'Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.Exception Details: System.ArgumentException: Item has already been added. Key in dictionary: 'RegEx'  Key being added: 'RegEx'

This if followed by a long list of items.

This occurs even on the public site not just the Admin side.

I have the same issues too. Sometimes the site loads quite fast and you don't pay attention to it, but sometimes it's really slow and the front end pages load slow too (approximately 5sec / page load). Then I have sometimes that same error message too, about RegExp.

My store is not published yet so it doesn't have any other user than my self. And the server is quite powerful.

Thank you for your help in advance.

And thank you for a great software!

The regex thing it's a known problem of the urlRewriter. It happens when the site is accessed in the first time (or appPool recycles) and the urlRewriter loads.
If two people access the site at this time or you clicked refresh when the urlRewriter still loading this error happens.
I think that we can move to IIS7 native url mapping instead of UrlRewriter DLL.

What do you think about IIS7 rewrites? Will it make the site load faster?