My registration page throws the error in Subject only on 1 of 5 URL when the www prefix is used and ONLY with the Chrome browser version 9.0.597.84.  No error if browser Firefox or IE is used.  Below is the DNN event log info.
I am using UCanUse module so I can get the ZIP code.  They indicate it is DNN site problem.  I have checked IIS and all the other pages have no error.

            ModuleId: -1
ModuleDefId: -1
FriendlyName: 
ModuleControlSource: 
AssemblyVersion: 5.4.2
PortalID: 0
PortalName: My eMarket Places.com
UserID: -1
UserName: 
ActiveTabID: 273
ActiveTabName: Registration
RawURL: /Registration/tabid/273/Default.aspx?returnurl=http%3a%2f%2fwww.myemarketplaces.com%2fHome.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer: http://www.myemarketplaces.com/
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.237 Safari/534.10
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 921d2350-7291-4329-93d5-d47e4d25c3cd
InnerException: Object reference not set to an instance of an object.
FileName: 
FileLineNumber: 0
FileColumnNumber: 0
Method: DotNetNuke.UI.Containers.ActionBase.get_ActionRoot
StackTrace: 
Message: DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.UI.Containers.ActionBase.get_ActionRoot() at DotNetNuke.UI.Containers.ActionBase.Page_Load(Object sender, EventArgs e) --- End of inner exception stack trace ---
Source: 
Server Name: EMARKET1