It would be interesting to check the cpu responses/heat/wattage after about 5 hrs. If it tends to crash/self-reboot after 6 hrs, keeping a monitor upon what's happening with the cpu 'might' lead to some guides toward the problem. It may have been a stuffy ram piece, or anything. A unreliably sized heat-sink is a possible cause 'if' it is a heat issue. It might also be related to how you use LW although that is purely the catalyst & not the underlying fault.

Some defenses against LW being a catalyst to the problem:
1. Tip: Purge the Downloads Queue!

2. Reduce drag on LW & if necessary reduce no. of files shared if 1,000 or more.

3. See the following link & follow all the off-shoot links to find hints & extra skills to help: To continue files downlding (click on link)

(I must'a had this window open a while b/c I didn't see Grandpa's response! )