Hmmm ... I had that issue. And still do at times. You need to reduce your upload bandwidth to allow your browsers to operate. If extreme, then even knock back your downld bandwidth a tad. If you run as an ultrapeer then it will probably be even worse. During those occasions you might want to temporarily disable your UP capabilities. (Tools>Options>Speed & tick the Disable UP capabilites. And press the Apply button.

By the way, one way to reduce drag on your system, close any LW windows you don't need open at that time. eg: Just keep the Search window open. Set downlds to Auto-clear. Delete any search results that are more than several hours old. And dare I repeat it, don't use the Resume/Find Sources function on too many (if any ) files b/c it has side-FX such as using up all of LW & your comp's resources if you apply it to too many files.