I got about 20 of these errors on my log. Any idea what is causing it?

AssemblyVersion: 04.08.01
PortalID: 0
PortalName: Lehigh Acres Live
UserID: -1
UserName:
ActiveTabID: 36
ActiveTabName: Home
RawURL: /linkclick.aspx?fileticket=kj5whvsxq5s%3d&tabid=36&mid=625
AbsoluteURL: /linkclick.aspx
AbsoluteURLReferrer:
UserAgent: dragonfly(ebingbong#playstarmusic.com)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 2c216a42-d994-439f-81d9-beb376ac13a4
InnerException: Unhandled Error:
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.Number.StringToNumber
StackTrace:
Message: System.Exception: Unhandled Error: ---> System.FormatException: Input string was not in a correct format. at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) at DotNetNuke.Services.FileSystem.FileServerHandler.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) --- End of inner exception stack trace ---
Source:
Server Name: MICRO113

Dragonfly is an indexing bot. You can ignore the errors

Rob

I also get heaps of these errors from robots on multiple DNN installations, mainly when using the core documents module on a page. Does anyone know if there is a way to stop getting this error reported in the log? I have tried blocking access to linkclick.aspx in our robots.txt but this seems to do nothing. Any help is appreciated.

Thanks