You could try to start Limewire by commandline with the following arguments:

java -Xmx255m -jar LimeWire.jar (in the Limewire directory).

it seems LW runs with the default heap-limit of 64mb (+ ~16mb for java-runtime itself) and of course if LW gets too close to this limit java is Garbage Collecting over and over which affects performance and could even lead to a crash of LW :-(

good luck, lg Clemens