That's sounds to me like a browser issue. Which browser and version of it are you using please? Which browsers and versions of them are your cisitors using? Please be sure that your have gone through the troubleshooting suggestions below and if your problem still persists please report it to Staff.
1. Some issues that you encounter with your WordPress.com blog or account can be solved by changing your browser settings, refreshing the page, or clearing the browser cache and cookies. See here > http://en.support.wordpress.com/browser-issues/ The instructions for specific browsers are found here > http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=32050
2. Some issues can be resolved by using another browser? If you haven't tried another one and your readers haven't either then I suggest that you do.
3. Some issues can be caused by not updating your Flash. You and your visitors can use this link to see if your flash is up to date. http://www.adobe.com/software/flash/about/ If it’s not then go to http://www.adobe.com/products/flashplayer/ and download and install the latest version of flash.
4. Lastly, when contacting Staff in order to avoid a time delay in finding a solution and applying it please do not forget to include details in your support ticket. Staff need to know what operating system you are using, which browser and version of it you are using, if you tried another browser or not and what the results were, whether or not your Flash is up to date, and how you are connecting to the internet and to wordpress.com.
Supplying these details up front in your support ticket means Staff won't have to employ back and forth email exchange with you in order to obtain relevant details and that means they can identify the source of the problem and provide a solution quickly. Here's the link for filing a support ticket with Staff > http://en.support.wordpress.com/contact/
Best wishes for a happy ending. :)