USB Redirection on Speech Mike not working on Client 4.x

I'm running into USB redirection issues on our dictation speech mike III. The mic shows up fine on the Windows 7 PC, but when you connect through the Horizon client into our Windows 7 VDI, it errors.

Not working:

Client version 4.1.0 build 3977225

Agent version 6.2.2.3508800

We've been using the SpeechMike with client version 3.5.2-3150477 without issues with the same agent as above.

Any ideas? Did a security parameter change? I've googled around, but no luck.

Thank you in advance for any help,

Rob