We would appreciate if you can use the "output speed throttling" feature of the YubiKey to slow down the character output from the YubiKey and try again. You need to use the YubiKey configuration utility to slow down the character output rate. The YubiKey configuration utility and the user guide can be downloaded from the following link:http://www.yubico.com/developers/personalization/
Please note that you need to reprogram your YubiKey in order to slow down the character output rate.
We hope this helps!