Never use the Force Resume function unless an absolute last resort!!! This will result in such issues. Are you sure it's the exact same file that's started to dwnld the next time you open LW? The best way to check is to look at your incomplete folder & see the sizes & modified dates of these files. I often had that issue with earlier version of LW but it wasn't the same copy of the file (despite the same name ... but from a different source that LW saw as a different file!)

I suppose just before you close LW, make a copy of both your limewire.dat & bak files & then re-add them to your incomplete folder before you re-open LW.