Unity 4.5 defines a new Tooltip attribute that can conflict with Playmaker's Tooltip attribute.
All built in actions use the HutongGames.PlayMaker.Actions namespace, so they find the correct Tooltip attribute.
Third party actions that use their own namespaces will need to point to the correct Tooltip.
For example, you can add this to your using statements:
using Tooltip = HutongGames.PlayMaker.TooltipAttribute;
NOTE: If you change an action's namespace it will look like a new action to Playmaker and parameters will be reset. So "using Tooltip..." is a better solution for existing action, while "namespace HutongGames.PlayMaker.Actions" should be used for new actions.