Comment 23 for bug 1335492

Here's the rationale for the rc files:
The .rc files are how Xfdesktop sees the space left on the screen. Things like the xfce4-panel may reserve space and xfdesktop respects that. The overall idea is that if your monitor goes through a couple resolution changes when your PC starts up or if you decide to play a game then your desktop should return to its old layout when it goes back to that resolution. Same thing with multi-monitor changes; you can have different layouts when your laptop is docked. The downside is that Xfdesktop doesn’t know when an icon position change should invalidate the other saved resolutions so in that case icons may change positions but Xfdesktop tries to minimize those moves.

Is it just one icon that gets messed up or all of them do? It may be due to something changing that causes xfdesktop uses an older .rc file (different panels or something like it on the desktop).