The majority of programming is not knowing a language, it's being able to approach problems and solve them using the language you're working with effectively, you can know the language inside out but if you don't understand programming it'll get you no where. For this reason it's okay to start with any language, granted some languages are awful and teach bad practices but a lot of programming is understanding methodology and not knowing a language, although that helps. This is why people can pick up a new language in a few days if they're a good programmer.
If you feel comfortable with starting with Actionscript, go for it, it won't put you at a disadvantage, it should be about what you want to achieve; if you want to make flash games then go for actionscript, if you want to make a standalone game go for c++ etc.