Update: We’ve cracked this problem! Upload should work on the site even with Flash 10. Uploading through LinkedIn will still have trouble if you have Flash 10, but we’re working on fixing that soon too.
As many of you have let us know, there is a problem with the upload button. Some of you have reported that you click on it and nothing happens. This is an issue with Flash 10. Adobe recently released Flash 10, and many of you have upgraded. The SlideShare upload button depends on Flash 10 and we are working to support Flash 10.
In the meantime, you can
-Downgrade to Flash 9 (Adobe has earlier version of Flash here)
-Use Single upload instead of Bulk Upload
Apologies regarding this inconvenience. We hope to have this fixed by tomorrow morning. In the meantime, thank you for your patience.