phpBB3 import to VB 3.7.3 problem

[adslthailand]

I can smoothly import by using impex.
But when I trying to import post, my phpBB database have more than 300K posts, I stuck and showing this message:

--
Importing 100 Posts

From : 215805 :: To : 215905


Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
Failed :: Post not imported
--

How to fix this problem....
Thank in advance.