After forced shut down iosx does not accept the password on the mcbook air

Hi there,

I cannot login into the mcbook air after having to force a shut down.

- While surfing with Safari, the mcbook froze for a longer period of time.

- We forced the shut down pressing the on/off button.

- After rebooting, we have a grayish screen with the apple logo, the user name, the password field and in the bottom three options: idle mode (rest), restart & shut down.

- When the password is entered, the wheel shortly turns and the mcbook stays with the same login screen without letting me enter the mcbook.

- When using an incorrect password the password-field shakes.

I tried booting with CMD + R and did check the volume and the access rights. Both showed no failures.

What could I try next to fix the problem? Ideally without having to set up the mcbook from scratch and losing the settings and data.

I do not know the exact IOSX status. It was bought in Nov-2012 and updated once since then I assume it is Snow Leopard

Thank you for your help!

Regards

Lottchen2007