http://www.webmasterworld.com/website_technology/3711575.htm
Read the whole thread and learn. SSL can only protect savvy users. Depending on how sensitive your data is, this can still be a problem.
Combining this with DNS poisoning would be particularly bad.
The SSL problem is mutual key agreement between two related parties communicating for the first time, and it's an easy one to solve.
There is a really persistant meme that SSL breaks when the DNS breaks, because all that happens when your certificate doesn't match or verify is that you get a warning. That warning says SSL isn't working anymore. You're not supposed to click through it. Real applications that use SSL under the hood don't pop up warnings: they freak out and quit.
You're talking about users who can be tricked into what are essentially non-SSL or degraded SSL (certificates from untrustworthy authorities) sessions, because they misread the URL bar or ignore warnings. That's a legitimate concern, most users are easily tricked, but that's not a vulnerability of SSL itself.