Actually, while there are some software updates available from laCie for Lion compatibility, TimeMachine is not among them, I think.
The linked LaCie support page says
"Cause: The LaCie NAS OS does not support Time Machine with Mac OS X Lion.
Solution: Use Mac OS X 10.6.x or earlier when using Time Machine to back up your Mac to a LaCie network hard drive."
(Which I find to be an extremely poor answer by the way).
On the other hand, I read on a WD support forum that they're working on a solution, and a firmware update for the WD live NAS series should appear in the next few weeks.
I have a LaCie Big5 NAS and LaCie is saying it may not be fixed!!