Problem w/ intricate drawings

One of my students has started an anime-style animation but has bogged down on the first intricate drawing, which causes TBS to slow down to an unendurable pace. We’re using an iMac 1.83GHz PowerPc w/ 512MB memory. She used the pencil tool rather than the brush in an attempt to minimize file size. Any idea what the problem could be? (I can get the file size tomorrow if you need to know.) Would more memory solve the problem? This is the first time any of the students has managed to slow down TBS w/ their work.