Kernel 2.4.20 has a ton of issues with gcc 3.3.
Apparently gcc 3.3 removed support for a bunch of deprecated features (or maybe it's just pickier than old gcc versions), and the kernel uses those features. Multiline strings is one of them.
There was a patch posted to lkml a while back that fixes certain issues.
2.4.21-rc6 (the latest as of today) also has a few compilation fixes for that compiler. You might try that kernel.
Which distro is shipping with gcc 3.3, BTW?