First & foremost reason for this is Apple's Java is not as good as Sun's Java that all other OS's use. Bad practice is also contributing. Don't use the Resume/Find Sources button on all incomplete files. This can have side-fx such as affect LW's connection quality. May queue your files for much much longer. This will also stress LW & your comp. such as freezing. If you use Resume/Find sources then just apply it to a couple or so at one time.
Better practice is manually search the files again. Else, control-click them in the download window & choose search for ...

Also, when upgrading to Pro, it's recommended to delete your preferences folder. Only do this whilst LW is CLOSED. Prefs folder is found here: /Users/your_username/Library/Preferences/LimeWire

Something else to help, don't let your incomplete folder get too many files. Occasionally, do this Tip: Purge the Downloads Queue! (click on blue link)

BTW LW has introduced a function where it automatically searches for sources for incomplete files every 30-60 mins or so. So really your approach is not necessary.

Nice to hear from you again jordan2. Been a long time. Good to see you have finally upgraded to OSX.