The installation of patch 118966 introduces this problem. See 6339315: Bad Compiler Induces IBM BladeCenter HS20 Resets for more information.
Description: The absolute mouse type event is not delivered to the Xorg server startup during a hot-plug of a mouse in a system. As a result, both of the mouse pointers are not located in the same position on the screen. When you move the mouse, the mouse pointers diverge further away from each other. The divergence between the two mouse pointers depends on the X server resolution.
Workaround: Download and install the latest revision of patch 118855 or install at least the Solaris 10 OS 11/06 OS.