After logging in SL, after a few minutes (depending on the environment), a gigantic lag occurs (drops to <1 fps) and nothing practical like walking, clicking something, ... can be done anymore. After some experience, you can predict the circumstances. It's always environment with a lot of photorealistic textures like paintings, shop displays, ... Places without these kinds of objects (not very much around, mostly sparsly built sim's) don't give the problem. There are ways to fix the problem. Its by unlocking the advanced menu and go as quickly as possible to it and go to render -> disable textures. If you were quick enough and the texture types giving the problem weren't loaded yet, you won't have the problem. If the problem occurs, sometimes disabling flexi's (ctrl+alt+shift+2) might solve the lag. Disabling all textures (ctrl+alt+shift+9) always solves it, but isn't really much of an SL experience anymore. Renabling the features you disabled will restablish the lag. To solve it for good when it occurs, I can disable textures, clear my network cache, tp away and back. The 'bad' textures will be gone then and not loaded due to the disabled texture option. However, these are workarounds. The disabled texture option will still show textures, but a light version of them. Photorealistic textures will be blurry and this makes it unusable in shops where you need to see the full detail. Therefor, I can only walk around in shops for maximum 10 minutes before the lag hits and I need to leave the shop. This makes it virtually impossible for me to shop.