I came across the latest release of WinHTTrack/HTTrack 
which is 3.20RC1 and I immediately downloaded and installed 
to try it out but it is still giving me the same problem.

1. Downloaded attachments (Word, Excel, Powerpoint, PDF) 
are not complete.
2. Application hangs when downloading those attachments. No 
matter how many times you try / restart the application, it 
will stop when reaching certain time of download.

Hope someone can help! Thanks.