We became aware of an issue earlier today that is causing the mutli variation listing tool to hang up and display a "Processing" message in Internet Explorer 7.0 so. Therefore, if you are using Internet Explorer 7.0, you are most likely being affected by this issue.
Assuming this is the case, since the issue in specific to Internet Explorer 7.0, you should be able to work around the issue for the time being by upgrading to Internet Explorer 8.0 or by using the Firefox browser. The Firefox browser can be downloaded free of charge from http://www.mozilla.com
I responded to your support case earlier today but the error you reported did not appear to match the behavior we have seen with respect to the issue described here. I'm now under the impression you are most likely being affected by this particular issue, but feel free to follow up with me through your support case if it does not sound like that is the case.