Re: [Bug Report] KDE4 Plasma looses theming and fonts with 180.44/180.51/185.19
It's pretty unlikely that this is caused by a memory leak in the NVIDIA driver. More likely, plasma is leaking pixmaps or client-side X resources. A good first step would be to determine which process has the leak: when the errors start occurring, does top report a lot of memory allocated to the plasma process? Likewise, please run xrestop and see how much memory it attributes to the plasma process.