The ASP.NET account (aspnet or Network Service) needs write access to the directory in order to generate the thumbnails. See the http://www.episerver.com/en/EPiServer_Knowledge_Center/Documentation/TechNotes/EPiServer-Operators-Guide/#File%20Access%20Rights for more information. /Steve

Just noticed that we are having the same problem. The thumbnails are being generated just fine under Util\Temp\thumbcache but when choosing Show thumbnails in the file manager we just get a broken image. Could it be that it's pointing to the wrong folder when showing thumbnails or something like that? Any help would be appreciated. /Martin

I'm pretty sure this is a permissions problem. I've never had - or heard of - a thumbnail cache problem that was not related to security. Try FileMon from System Internals to see if there are any permission problems with the files under /util/temp /Steve

OK, I've used Filemon to see if that can show anything that's wrong. Can't say I'm an expert at Filemon but I can see that it is requesting files from the thumbcache-folder and the result is always success, but still I can't see the pictures in the file manager. By the way, I'm using the Unified File System feature to store my files, if that can have anything to do with it? Best regards /Martin

I have also used filemon, which shows its successfully opening and reading the correct images in the correct directory, while attempting to load the thumbnails in the file manger. I have checked the ASP.Net permissions to the directory, and it has both read and write access. If the permissions is the issue how can it be able to create the thumbnail images? I would be grateful for any further ideas?

Just took one more look at this problem which I haven't been able to solve. Used Fiddler to see if that might give some more information, can't say I understand Fiddler that much but here is what happens. Checked the "Show thumbnails" checkbox and then the following URL gets called (for an image called hermes.jpg): /Util/Image.aspx?width=50&height=50&src=%2fDocuments%2fhermes.jpg. The response code is 200 (OK) but the content-type is "text/html" which seems a bit strange? If I take that URL and try to call it directly in a browser I just get gibberish in the web browser. Doesn't make much sense and I'd expect to get an image back when calling that url, isn't that correct? The image.aspx doesn't give much help either unfortunately since there is no code-behind file for that aspx in the EPi-project. Would really appreciate if someone could help us solve this issue. /Martin Emanuelsson

Richard and everybody else, Finally I believe I've managed to nail down this problem and what the cause for it is. I'm using ASP.NET AJAX on my site and for that to work with URL rewriting we've had to implement a HTTP Module which you can see here: http://www.episerver.com/en/EPiServer_Knowledge_Center/Developer-Forum2/EPiServer-Developer-Forums-/1805/10539/ Now I've noticed that this causes the thumbnails in the file manager to break, took a while (and quite some "filemon-ing" and "fiddler-ing") to realize this connection. To solve the problem I've changed the HTTPModule so that it only acts when the contenttype is "text/plain" and not "text/html". Perhaps this is something that you're using as well Richard? Perhaps there is another way to make both ASP.NET AJAX and the showing of thumbnails to work? If so I'm really interested to take part of it. Best regards Martin Emanuelsson Guide

Yes our solution does implement an http module also and we had also narrowed the problem down to this, however we hadn't determined how to resolve the conflict between the module and the thumbnails. Thanks for the info, we'll try it out. Rachel - Richard's colleague