Hi, i can certainly sympathise with you, this problem was a nightmare for me as well, exactly the same thing happened to me and it was a few days before everything was ok again. Your avatar photo is how my avatar looked as well, i just had my head poking up from the ground all the time no matter where i went, but i dont think my legs had collapsed underneath me, because i tried editing my avatar to raise him up using the hover slider (this is on the firestorm viewer, im not sure if the SL viewer has this) he raised up ok and i could see his whole body above ground, but when i saved it, he sprang back down underneath the ground again, the edit didnt save. welll this is what i done which seemed to correct the problem. before i logged off i left my avatar in fly mode, then when i logged on again, i logged on at a different location on the ground, my avatar rezzed up above the ground because i was still in fly mode and when i landed i landed on the ground and was perfectly ok after that. so i recommend you try the same as me, but if that fails then maybe a character reset going back to the default avatar. Good luck, i hope it works for you, i know how awful this problem is, its impossible to enjoy SL otherwise.