Do you have a 2005 OB automatic 2.5i?
The CEL coming on and cruise light flashing may be a common problem on a certain batch of these 2.5i Outbacks, according to a local Subaru service shop. Another symptom may be surging while in cruise control.
The fix (under warranty) is to have the service shop get the ECU ID #, obtain the appropriate cartridge from Subaru, reflash the ECU and replace the front fuel/air ratio sensor.
This has just been done on mine and has solved the problem for good - I hope!