There is a bug in VMware Fusion 2 Beta (Beta 1 and Beta 2) that results in spontaneous reboots without even throwing a kernel panic. The problem occurs only when powering up a virtual machine after the Mac has been waked up from sleep. Especially Mac Pro users seem to be hit by this defect.
According to
this thread some people found out that it helps to reload one of VMware's kernel extensions after wake up to workaround the crash until VMware has a fix ready.
Because this is very prone to be forgotten I automated it by the following steps:
1. Install
SleepWatcher (both PKGs in the DMG)
2. Add the following three lines to the end of /etc/rc.wakeup
LIBDIR="/Library/Application Support/VMware Fusion"
kextunload "$LIBDIR/kexts/vmmon.kext"
kextload "$LIBDIR/kexts/vmmon.kext"
Update: It's fixed in RC1