Are you using the latest version from the new plugin's database (http://moodle.org/plugins/pluginversions.php?plugin=format_topcoll) as I have done a lot of effort to make it work with IE etc. - the version in the old plugin's database is redundent. This version requires Moodle 1.9.14 - but may work with Moodle 1.9.9. In the topcoll folder there is a file called 'version.php' for which you may have to change:
$plugin->requires = 2007101591.06; // 1.9.14
$plugin->requires = 2007101590.00; // 1.9.9
to allow it to work.
I have tested with IE9 (version 9.0.8112.16421) on Moodle 1.9.14 (Build 20111102) with the standard white format. I could possibly test with 1.9.9 but that would take time as I would need to create a new installation for it.
If that fails, please could you provide a screen shot of the error and even zip up your 'topcoll' folder and attach so I can see what version you are using and attempt to replicate the issue.
I've just done a test with Moodle version 1.9.9 (Build 20100721) using the only version of Aardvark Pro I could find (http://moodle.org/mod/data/view.php?d=26&rid=2913) and it does work with the latest Collapsed Topics for Moodle 1.9 on IE 9. You do indeed have to change the version.php file as stated above in the 'topcoll' folder - I've attached to help.
Just realised I could have given you the complete code!! Please find attached to replace yours.
Very strange as CT has unique css. I think I need a copy of your full Aardvark Pro theme in order to test properly to avoid any inconsistencies in the version you have and the version I have. Then I would be able to use Firebug to see what is going on. In tryin to integrate the css you sent with the version I was able to get, there are some differences in the naming and pathing contained in the files, so definately need a copy of your theme to test or guest access to your site with a CT course.
I will message you an eMail that can take this size of zip file.