First I want to say that this problem has been reported by me too in the past... After loosing for 2 times the download progress for a 700 MB file I decided to test this program at it's limits. (Atention: I'm not a beta tester or whatever...! and I use WINDOWS !!!) So here are my advices:

There are 2 major possibilitys to lose your download progress. In each one of them when you saw the error is to late...!!! and I STRONGLY recomend you not to continue a download when you saw that it has jumped back more than 1% - 5% - 10% (deppending on your file size)... 'cose is only time loosing... in the end you'll get a popup asking you if you want to continue the download because LW has detected corruption in the file... So you have to take some precautiones!!!




POSSIBILITY 1: You paused all downloads, closed LW, (ShutedDown or Rebooted...) and when you came back the download progress goes back (even to 0% sometimes) or the LW puts up a popup saying that it has dectected corruption in your file, asking you if you want to continue the download... It's too late... (remember?)

Precautiones Advice: In this case you have more chanches to recover your download progress... Every time you exit LW for some reason (and you let paused downloads) do a ScanDisk of the drive (partition) wich has the beeing downloaded files located on... or if you forgot do it BEFORE starting, again, LW... If you got the error saying that windows seems to report more free space than it really is, than let ScanDisk fix this error !!! (and you can be a happy man 'cose you just saved your downloads...)




POSSIBILITY 2: You have a sys. crash or LW crashes... and when you came back the download progress goes back (even to 0% sometimes) or the LW puts up a popup saying that it has dectected corruption in your file, asking you if you want to continue the download... It's too late...(sorry again... remember?)

Precautiones Advice: In this case you have less chanches to recover your download progress... but for me it worked every time and belive me I crashed that system so hard that even the Microsoft didn't thought that this methods are possible... So here is what to do:
Precautiones A: When your sys or LW is crashed don't reset (by button or by Ctrl+Alt+Del) your system. First try to STOP your internet connection from the firewall (if you have one and if it is still possible). If it's not possible try to stop the connection by shuting down the (cable) modem. NOW WAIT ABOUT 1-2 MINUTES before rebooting! (remember your sys. or LW is crashed and every operation is verry slow...) It seems that most of the times when you have a sys. crash or an LW crash, the core of LW is still running "normally" in background (and only the interface <based on java> is crashed). So by doing this LW will automaticly pause the active downloads ('cose you have no internet connection anymore...)
Precautiones B: After rebooting DON'T FORGET to do ScanDisk !!! and if you get the error saying that windows seems to report more free space than it really is, than let ScanDisk fix this error !!! (and you can be a happy man 'cose you just saved your downloads...)





NOTE: ScanDisk has a checkbox :Automatically fix errors. By default this is unchecked... but if is checked then the ScanDisk will fix the errors without asking anymore... Now if you really don't know what the solutions may be to other errors that may appear check this box before starting ScanDisk. But I recomend to fix errors manually to those who know...(at least how to recover a lost file with ScanDisk)

I tryied this methods on my system on files betwen 10MB and 750MB with progress betwenn 25% up to 75% and it always worked FOR ME. Now all that I can do it's hope that you never experience such problems... but if you do (you'll be glad if you had read this before)... try my advices and may be it will help... Good Luck !!!