even worse:
after creating a new topic and receiving the described error, I can no longer acces the Web App at all:
-------------- error message -----------
Input string was not in a correct 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.FormatException: Input string was not in a correct format.
Source Error:
Line 112: <asp:Repeater runat="server" ID="LatestPosts">
Line 113: <ItemTemplate>
Line 114: <a href='<%#yaf.Forum.GetLink(yaf.Pages.posts,"m={0}#{0}",DataBinder.Eval(Container.DataItem, "LastMessageID"

)%>'><%# yaf.Utils.BadWordReplace(Convert.ToString(DataBinder.Eval(Container.DataItem, "Topic"

)) %></a>
Line 115: <a href="<%#yaf.Forum.GetLink(yaf.Pages.posts,"m={0}#{0}",DataBinder.Eval(Container.DataItem, "LastMessageID"

)%>">
Line 116: <img src="<%# GetThemeContents("ICONS","ICON_LATEST"

%>" border="0" alt=""></a><br />
Source File: c:\Inetpub\wwwroot\YAF\pages\forum.ascx Line: 114
..... ( do you need the stack trace ??) .....
-------------- error message -----------
it seems the database is corrupt:
the new topic in Table yaf_Topic has LastMessageID set to null
Ina