At least once a week, someone on the Performance team will get a customer call concerning hangs or resource depletion on their file server.  The file server in question is used for user home folder storage and users are accessing Outlook Personal Storage (.pst) files stored on the server from their client.  The issue will manifest as either a server hang, or PagedPool depletion (Event ID 2020).  Oftentimes the issue will occur first thing in the morning - when users are logging on and launching Outlook.  In especially severe cases, the issue occurs several times daily.  Sometimes the server will hang for a few minutes and then continue operating for a few minutes - and then hang again.  Rinse & repeat.  The users are frustrated because of slow access to their data, the server administrators are frustrated because they are tasked with fixing the problem, and upper management is frustrated because everyone else is frustrated.

If you're in this situation - there's good news ... and very bad news.  The good news is that this problem is very common and is a known issue.  The very bad news (from the customer's standpoint) is that PST files on a LAN/WAN is an unsupported configuration.  Some customers are very surprised to hear this but Network Stored PST files have been unsupported since the days of Exchange 4.0.  Microsoft KB Article 297019 goes into some detail about the effects of Network PST files:

Full story: http://blogs.technet.com/askperf/archive/2007/01/21/network-stored-pst-files-don-t-do-it.aspx