Version 04.05.04 - When I try to delete a user I get an error "Error Deleting User" and the following in the event viewer:

THREAD ID: 8
TYPE: DotNetNuke.Entities.Users.PurgeUsersOnline
EXCEPTION: Input string was not in a correct format.
RESCHEDULED FOR: 8/8/2007 10:26:12 AM
SOURCE: STARTED_FROM_BEGIN_REQUEST
ACTIVE THREADS: 0
FREE THREADS: 1
READER TIMEOUTS: 0
WRITER TIMEOUTS: 0
IN PROGRESS: 0
IN QUEUE: 3
Server Name: Server

and

AssemblyVersion: -1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider:
ExceptionGUID:
InnerException: Input string was not in a correct format.
FileName:
FileLineNumber: -1
FileColumnNumber: -1
Method:
StackTrace:
Message: 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.Entities.Users.UserOnlineController.GetOnlineTimeWindow() at DotNetNuke.Entities.Users.UserOnlineController.UpdateUsersOnline() at DotNetNuke.Entities.Users.PurgeUsersOnline.UpdateUsersOnline() at DotNetNuke.Entities.Users.PurgeUsersOnline.DoWork()
Source:
Server Name: Server

Teh user is not deleted. Any help resolving this is appreciated.

Thanks.