You can pull the card out yourself with a pair of needle nose pliers or sometimes with your fingers, if you have strong fingernails. Once the card is pulled out, try inserting the paper clip again to release the spring mechanism. If you hear the springs release, you can try inserting the card (or a different card) again. Of course, the issue may recur.

Inspect the card for any obvious physical damage, large scratches, or other irregularities. If the ejection issue recurs, especially with various cards, you should have your PCMCIA Expansion Module or PowerBook inspected by an Apple Authorized Service Provider or returned to Apple by calling 1-800-SOS-APPL.