unable to sign into iTunes store...java error

Hi, when I try to sign in to my iTunes I get this error.
java.lang.outofmemoryerror: java heap space

I just bought an iMac and transferred all my iTunes files to this computer. I have authorized it and it is one of two computers currently authorized for purchases. Since I can't sign on I can't purchase either. I requested a change to my password, which I "changed" it to the password I was always using, still no results. Any suggestions?