I have a customer who uses very specific view columns, color coding, and ordering to go with some custom addins. Every couple of months, his default view settings saved under "userdefaultview" will revert to default for no apparent reason.

Windows updates are not causing this as there is no time correlation. 

System restore has worked once in the past, but is not working right now.

User is on Outlook 2013 connected to Exchange 2010 through an onsite server. He only uses one onsite desktop, and remotes in with other devices due to the large amount of customization on his Outlook client.

Thank you.

since Outlook 2003, the view settings information is stored in the mailbox or PST file. it may be difficult to determine the root cause because this issue happens every couple of months. the cause may lie with the client side or the server side.

to work around it, try to back up the custom views to a pst file which we can use to restore the views if this issue occurs. see:

http://www.outlook-tips.net/how-to/copy-outlook-custom-views/

after the backup, we can also try starting outlook with outlook /cleanviews and wait to see if it will fix the issue.