Hi ecmallory,
Thanks for posting about the problem you have encountered here. There is a known compatibility issue between Internet Explorer 9.0 and the older version of the description editor available on our site which causes the behavior you have described when the spell check and a number of other buttons on the editor are used, so I suspect you are running into that problem.
Assuming that you are using Internet Explorer 9.0, all you should need to do in order to avoid encountering the same problem moving forward is change your account preferences to use the new Design Editor v2.0 that is now available.
In order to do this, you will need to mouse over the “My Account” tab within your account, select the “Acct Preferences” option under “Settings”, check the box next to “Use Design Editor v2.0” in the Listing Management section of the ensuing page, and then click the “Update Account Preferences” button below.
I hope this helps. If you need any further assistance with this, please feel free to contact our customer support team by mousing over the “Help” tab within your account and selecting the “File Support Case” option.
-Mike