Still exists in AutoCAD 2011. My my guess is either file-path length or it just doesn't like network mapped drives.
... Try using the UNC path instead of the mapped drive letter. It seems to work...sometimes .. Good luck
Interesting. I've been struggling with this for several months with 2010 and 2011. Yesterday I removed Computer Associates "Total Defense" anti virus software and firewall. Today, when I logged on all my network shorcuts showed up again in Design Center. Coincidence?
I have tested both AutoCAD 2011 and 2013. If I use a network path assigned to a drive letter it works. If I use an UNC path it will fail.