Under Help/About Internet Explorer, what is you cipher strength number.
If not 128 check this site for possibly solutions.
http://www.colba.net/~hlebo49/digsigna.htm
If you were able to get to your bank before and now get this message what
did you install in the area of firewall or security software?
Just in case you need this.
Some Web Site Services Do Not Work After You Upgrade to Internet Explorer 6
Some Web site services may not work properly after you upgrade to any of the
versions of Internet Explorer listed at the beginning of this article. The
Web site may suggest that you need to enable cookies or upgrade your browser
to one that supports Java, frames, or other technology that is supported by
Internet Explorer 6.
For example, when you attempt to log on to, or use, a secure banking Web
site, you may be prompted to upgrade to a compatible browser or a different
version of the same browser.
http://support.microsoft.com/?kbid=302708