I found out some more details for those having the issue. The below information applies to desktops, but probably applies to mobile as well.
Working with several of our members, we have been able to identify a small segment where upgrading your browser may alleviate the problem. There is a limitation with Safari version 5.x (both Mac and Windows) that has to do with the amount of cookie data that the browser will store and the way it will retransmits this data back to the web site. Under several scenarios the web site will exceed these limits. When this happens the browser will only retransmit part of the data back to the web site. Because the data received by the web site is incomplete, the end result is that the web site does not recognize the member as begin logged in.
For members that are repeatedly seeing the issue and are using the Safari 5.x for Mac, we recommend upgrading the browser to the latest version, Safari 6.0.2 for Mac. This can be done via the Mac Software update utilities (http://www.apple.com/softwareupdate/
). Unfortunately for member that are using Mac OS 10.6 or earlier (Snow Leopard, Leopard, or Tiger) or members using Safari 5.x for Windows, Apple has not released Safari version 6 for the these platforms and has made no public announcements concerning any upcoming release dates. In these cases we recommend switching to one of the supported browsers; the latest version of Chrome, FireFox, or Internet Explorer (Windows only). Because we have not be able to definitely isolation the cause some member may continue to experience this problem even after upgrading.