Outlook 2010 hangs when importing PST file

"Connecting to pst-files located on a network share is not supported by
Microsoft as it can lead to poor performance, data corruption and even
data loss. As indexing is an I/O intensive process, the fact that Outlook
gets unresponsive for network connected pst-files is to be expected; keep
your pst-files on your local hard disk when you want to work with them in
Outlook "

http://answers.microsoft.com/en-us/office/forum/office_2010-outlook/outlook-2010-hangs-when-importing-a-large-e-mail/552bd4db-5255-4ef9-a351-d1ff9bef95a2?page=4

If you are working with a PST on a network share - expect problems. Rather
copy the file to the local HDD and import the data from there into Exchange.