RAM problems months after install

Has anyone had an issue with faulty RAM, months after installing it? I replaced the two standard 512MB sticks on my Macbook with two (matching) 1GB sticks, so essentially, doubling my RAM. The brand is Crucial. I installed the RAM in December '09. I shut down my Macbook this morning, unplugged it, put it in my laptop bag, brought it to work, turned it on, and got the beeping. It's two beeps, then a pause, then three beeps. I tried resetting the PRAM, did nothing. Any thoughts?