Sometimes when relogging or after a crash the placement of windows returns to the default.
For example - In R9, I have separated out my conversations from my nearby chat, and keep the conversations in the top right corner of my screen, while the nearby chat is bottom left. I always move my inventory floater and build floater as well.
In R8.1 the only time the inventory and build floater returned to default is if I'm logged out due to an internet connectivity issue. In R9 these randomly return to default with some logins having the placement remembered and some logins not. There doesn't appear to be a pattern as to what triggers the return to defaults.
CPU: Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz (2394.55 MHz)
Memory: 8080 MB
OS Version: Microsoft Windows 8 64-bit (Build 9200)
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: GeForce GT 630M/PCIe/SSE2
Windows Graphics Driver Version: 9.17.0010.2857
OpenGL Version: 4.4.0