Similar to #1079960: Advanced options that require return values do not work, the timeoutFn function is supposed to return a result. This doesn't work currently because of the use of eval. The fix is simply doing the same as for pagerAnchorBuilder; providing a returnVal variable which can be set by user code.
It defaults to the global value so hopefully it returns something sane even if the user's code has a bug.
Possibly there are some other functions that need this change too, but the JQuery Cycle Plugin documentation page isn't very clear about which functions are supposed to return a value and which are called purely for their side-effects.