This is probably because you have mod_security active on your server. To get the charts working you will need to disable it.
One way to do this by creating an .htaccess file in your root Interspire Email Marketer folder with the following contents:
<IfModule mod_security.c>
# Turn off mod_security filtering.
SecFilterEngine Off
# The below probably isn't needed, but better safe than sorry.
SecFilterScanPOST Off
</IfModule>
If this doesn't work you will need to contact your host.
