Ich habe ein problem

"ein" is "one" for male and neutral Nouns. (ein Auto, ein Mann)
"eine" is "one" for female nouns. (eine Frau)

For a more wholesome aproach I would advice you to read up on the grammatical cases. We have nominative, genitiv, dativ and accusative in german.

ein = when the word doesn t got a sex (das) or is maskulin (der)
Ein Auto , das Auto .. Der Mann , ein Mann

eine = when the word is fenimin (die)
Die Frau , eine Frau

the rest is better explain as Pronomen there are Nomininativ, Dativ ,Akusativ , Genitiv Pronomen you can ask in the sentence for them so you can see
what ending you need to choose here is link for esamples and explaination:

http://de.wikipedia.org/wiki/Possessivpronomen

Danke!