Window goes absolutely BLACK after 5-10 minutes of website shopping. Some site are more prone to hang Firefox...Amazon, Trivago and other known sites. Sometimes is will load next page in black blocks and then fill slowly. But that always heralds a full hang to come next. Unresponsive. NO error message. Must close the Firefox window and terminate Firefox entirely. If two or more Firefox windows are open, they must ALL be closed before Firefox will reload normally. Download history was cleared and I increased Firefox cach 250MB >>1GB with no benefit. It acts like a memory/cache management issue. Current Lenovo laptop PC with TONS of storage & memory on a SS Samsung drive running Windows 7. Same events are occurring with on another current family laptop PC running Windows 10. These events have NOT occured when using iExplorer or Chrome as browsers. Firefox v.51.0.1. This problem predates this version update. Please help. I would hate to dump Firefox after many years of trouble-free use.