Try with LW 3.8.5 and OS 10.2.8.

2GB of incompletes might be a bit much--have you considered cleaning out your incomplete folder?

Yes, some files can get stuck redownloading chunks (the developers are looking into it). The info on what chunk is downloaded is stored in the downloads.dat file in the incomplete folder, and backed up in the downloads.bak

Lose or corrupt either of those files and yes, you'll have to start again.

There is also a setting in prefs for the number of days to keep incompletes.