Here's a great excerpt from the panic.c file in Solaris/OpenSolaris:
114 * A Note on Word Formation, courtesy of the Oxford Guide to English Usage:
116 * Words ending in -c interpose k before suffixes which otherwise would
117 * indicate a soft c, and thus the verb and adjective forms of 'panic' are
118 * spelled "panicked", "panicking", and "panicky" respectively. Use of
119 * the ill-conceived "panicing" and "panic'd" is discouraged.
So remember this next time you're emailing someone about one of your machines "panicing".