Hi Bo,

Is this happening on your development machine or on a machine exposed to internet traffic? I've never seen this on my development machine but I have seen it on my production site logs. If you google this error you'll find lots of people reporting it and various causes and solutions.

It can happen from automated scans that purposely mess with viewstate. It can happen on web farms if you don't have the smae machine key in web.config for each node of the farm. It can also happen on single machines as I have seen posts in the asp.net forums about this. mojoPortal does have a machine key in the web.config which should prevent the most common internal causes but it can still happen form scan scripts, or if cpu useage gets too high and the application pool is getting recycled frequently.

I've been suspicious that some of the ones I see in my logs for this site might be related to bugs in Atlas but haven't been positive of this. I can't seem to produce this error on my dev machine.

Joe

If you look in the log4net.config file you'll see settings for the rollinglogfileappender, you can spacify how many log files to keep and how large the files gets before it makes a new log file. They are currently set like this:

<maxSizeRollBackups value="10" />
<maximumFileSize value="1MB" />

Joe