What's wrong with my video card AGP?

My new video card is 128mb 128bit. Sometimes when i turn on my computer it was only 64mb and sometimes 128mb. What's wrong? by the way my mboard is MSI and my video card is Inno3d.|||Without knowing exactly which card you have it will be hard to diagnose. If this was onboard memory I would say it was sharing memory, but being as it is a dedicated card for video, I will need to see the exact specs. What is the model number for the card?