Problem in Uploading to Arduino Diecimila from Windows 7/64 bit version

Hi People... Can anyone Help me out this.... I'm facing problem while uploading programs to the Arduiono Diecimila Board from the Windows 7 Ultimate 64 Bit version. The problem started from 3 days back before that it was working Good.When i upload the program below Message flashing....!

Binary sketch size: 1252 bytes (of a 14336 byte maximum)
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

And i've selected the Serial port correctly. Thanks in Advance.... :)

And one more detail is i'm using ATmega 168 on the Board 8)

Do you have the right board selected from the Tools menu?

Thanks Milllies For your reply... I did, i'm using Arduino Decimila Board i selected that.The Port too.