>I was able to resolve that issue by adding a MachineKey inside the Web.config. I usually do not have to do that but in a share environment under a very high security, this random 404 hits we keep getting at 66% of the time on /WebResource.axd was quite irritating. Maybe someone can explain that?

Presumably you set the decyrptionKey attribute to a fixed value?

As I understand it the querystring generated for the webresource.axd url is encrypted. If the encryptionKey on the server changes between the time this is done and the resource actually being requested then the decryption (and thus then request) will fail. Normally this should not be a problem since the time lapse between the two events is minimal (but might happen, for example, when a web crawler hits the site).

One obvious case where this would be essential is on a web farm - all servers would need the same key.

That said I don't see how this is related to having files located on a share.....