We updated in a few steps to DNN 6.1.2.

Now in a forum module we can´t upload a new attachement. It throws the following error:

ModuleId: -1
ModuleDefId: -1
FriendlyName:
ModuleControlSource:
AssemblyVersion: 6.1.2
PortalID: 0
PortalName: Addison Forum
UserID: 3
UserName: mwallner
ActiveTabID: 151
ActiveTabName: Forum
RawURL: /Vertrieb/Forum/tabid/151/ctl/PostEdit/forumid/111/postid/373/action/edit/mid/687/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer: http://addison-intranet/Vertrieb/Fo...fault.aspx
UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:9.0.1) Gecko/20100101 Firefox/9.0.1
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: e6032e82-505a-421a-8901-8f8a4f522596
InnerException: The underlying system threw an exception.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: DotNetNuke.Common.Requires.NotNull
StackTrace:
Message: DotNetNuke.Services.Exceptions.ModuleLoadException: The underlying system threw an exception. ---> DotNetNuke.Services.FileSystem.FolderProviderException: The underlying system threw an exception. ---> System.ArgumentNullException: Value cannot be null. Parameter name: content at DotNetNuke.Common.Requires.NotNull(String argName, Object argValue) at DotNetNuke.Services.FileSystem.StandardFolderProvider.AddFile(IFolderInfo folder, String fileName, Stream content) at DotNetNuke.Services.FileSystem.FileManager.MoveFile(IFileInfo file, IFolderInfo destinationFolder) --- End of inner exception stack trace --- at DotNetNuke.Services.FileSystem.FileManager.MoveFile(IFileInfo file, IFolderInfo destinationFolder) at DotNetNuke.Common.Utilities.FileSystemUtils.MoveFile(String strSourceFile, String strDestFile, PortalSettings settings) at DotNetNuke.Modules.Forum.WebControls.AttachmentControl.cmdUpload_Click(Object sender, EventArgs e) --- End of inner exception stack trace ---
Source:
Server Name: EUWNSD250001


What can we do?

Check your folder permissions. Make sure the Network Service account has Full Control over the Portals/{Portal ID}/activeforums directory.

Also, is your site running in medium trust? That has been known to cause issues in the past.

Active Forums - 4.3.8.0 Enterprise Edition
DNN Pro - 6.1.5

We're having a somewhat similar issue. We run all of our .NET websites in Medium trust (it is a custom medium though so we can add whatever we want). I've tried IE8/9, FF3/12, & Chrome 18 and in all of these the same thing happens. I choose the file to upload and then upload it but then get a popup saying "An error has occurred" which clicking OK on then wipes whatever you've done in the post. If you go back to the attachments bar and click My Files your file is there and I checked in the folder structure to see they are being uploaded. If you click the Add File to Post button you get the same "An error has occurred" message and it wipes your post again.

Oddly there's nothing being logged in the DNN Event Logs or the Windows Event Logs. I tried running it from the server as well but nothing useful was shown.