ExpiresActive causing error

Hi,

I'm trying to control the caching of my web content with the ExpiresActive
directive and the .htaccess file in the /public_html directory of my site.
I put the following lines (straight from the Apache manual) into the
..htaccess file but get the dreaded Internal Server Error.

ExpiresActive On # enable expirations
ExpiresByType image/gif A2592000 # expire GIF images after a month
# in the client's cache
ExpiresByType text/html M604800 # HTML documents are good for a
# week from the time they were
# changed, period


My host provider says that the mod_expires and mod_headers modules are
installed into httpd and says he doesn't know what the problem might be
since he is not familiar with the mod_expires directives. Can anyone help?
They are running Apache 1.3.

Thanks,
Steve Dondley