Nothing at all in the event logs, I noticed that twitterfeed could not read my RSS feed for the Events Calendar, so I investigated. Lauching it in IE produced a Server Error, but there was nothing in the Event Log about it. I played around with it a bit, it would work at 1 day but not 7 days (30 days was my original setting), so I worked up one day at a time and found 4 days was the maximum number of days it would show the RSS feed (I don't know if it is an issue with number of days or number of events).
So... I logged onto the server to see what the error was (only displays on localhost), and this is what I got:
Server Error in '/' Application.
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Value cannot be null.
Parameter name: format
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.ArgumentNullException: Value cannot be null.
Parameter name: format
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[ArgumentNullException: Value cannot be null.
Parameter name: format]
System.String.format(IformatProvider provider, String format, Object[] args) +7483153
System.String.format(String format, Object arg0) +43
DotNetNuke.Modules.Events.EventRecurMasterController.RecurrenceText(EventRRULEInfo objEventRRULE, String LocalResourceFile, CultureInfo culture, DateTime EventDateBegin) +482
DotNetNuke.Modules.Events.TokenReplaceControllerClass.TokenReplaceEvent(EventInfo eventInfo, String sourceText, Dictionary`2 dict, EventSignupsInfo eventSignupsInfo, Boolean addsubmodulename) +3060
DotNetNuke.Modules.Events.EventRSS.Page_Load(Object sender, EventArgs e) +4489
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627
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Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.3082
Edit: Sorry for the edits, the HTML wasn't displaying properly so I converted it to text.