New graphics card - taking ages to load PC now

Hi guys. i installed my new AMD 5450 1gb graphics card earlier, and ever since it takes ages to initially turn on upto the black and blue dell screen. Any ideas on why this is happening ?
Also, when i put the PC into "Sleep" mode, it goes to sleep but doesn't wake up... and i have to reboot the whole pc again,
Thanks

I have a dell inspiron 531