Hi Richard,
From what I've read at the other forum, LW 5 should automatically try to resume files (even though there's no 'resume' button any more & the incomplete folder doesn't show in My Library). And clicking on 'Search again' beside a stalled file should start a search & then the file can resume if sources are there.
It doesn't always work. Like I said earlier, sometimes a new search has kicked the download off where 'search again' hasn't done anything. And just now I tried another stalled download with a new search but the download didn't resume at all - even though I found a file that looks fine with 2 sources. The stalled download didn't budge but downloading the file from the new search results goes right ahead.
That's why I thought you might be better off at the forum where LW's developers post - they might be able to give you more info
Don't forget that you can revert back to LW 4 if you want to. If you're using LW basic, there's a page to download old installers:
Lime Wire » Download Out-Of-Date Installers
If you're using Pro, your personal download page has a link to 4.18.8 on the left hand side - click on 'Get LimeWire Pro Classic'.