FileBrowserSheet seems frozen while browsing network folders

Our customer complains about the FileBrowserSheet being unresponsive while browsing network folders.
I haven't been able to reproduce this in my development environment but I saw this in 'action' (or inaction in this case).
They click a folder then ... nothing happens, they wait, then wait. They are free to try other folders (I guess this is asynchronous task) but nothing happens.
I've asked them to navigate the same network path with the Windows explorer which has no apparent problem (some slowdowns at worst).
So, it's hard to say where the problems is (no stack trace) but there is a problem.
One first improvement that could be done would be to display an hourglass (busy cursor) while the current I/O operation is pending.
Another one could be also to set a timer after which the I/O operation would be canceled (or abandonned) and give back hand to the calling code.
That's all I'm thinking fo r now.
As soon as I can get some more info on the origin of the problem, I'll update this issue.

Cheers,
A.J.