I've read through the threads and don't seem to find my particular problem anywhere. My download speed had been erratic lately too but my primary problem is, once a file completes, it sits at 100%, with a reading of 0KB/s and continues to read that it is downloading.
If I try a pause/continue, I lose 20% of the file.
I am running LW 4.10.9 but have tried most of the different ones you have offered on here from 4.11.0 to 4.3.3 No change.
My OS is XP.
My ISP is Alltel in the US
Kernel32dll version is 5.1.2600.2180.
File path is short.
Plenty of space to save left on my drive.
Any help would be appreciated.
Thank you.

Also, if I cancel the download and retry, it sits at 100% and reads queued.
No firewalls interfering and there is no brick wall over my globe.

Whats the file? if its a video file or music file, just hit the preview, then copy the preview file out of the incomplete directory and rename it. Delete the downloaded file.