If you're finding your LW is getting sluggish, close it down. Then re-open it. Java on the mac is not that efficient. And unfortunately virtual memory which all osx apps use grows due to Java's inefficiency. If you are using Tiger, then update your Java to 1.5 & use the Java preferences to force LW to use 1.5; Setting up Java 1.5 Unfortunately, Java 1.5 is only available for Tiger OS 10.4

OK, that explains why LW is sluggish. Why is it unable to resume download from the last position saved? If the file was entirely in VM, that I could understand. But the file is on disk, as much of it as was downloaded before the crash. Yet LW isn't able to identify where it was in writing the file before the crash, and resets to zero. The buffer obviously wrote to disk before the app crashed. Why can't LW recognize it?
Even weirder, sometimes when I quit out of LW, I lose huge quantities of the file. Sometimes I'd be half-way through a dl, quit out of the app, and only be at 25% when I relaunch LW. What gives?