Depends what's actually happening, which is unclear as you've only provided a high level description of the issue. I.e. you have not confirmed whether stats show drops on interfaces, and if so, what those interfaces host.
Understand, due to the architecture of a 2960, there are certain situations that might only be corrected by using a "better" switch. Or, if the congestion is on an uplink, you might need one of higher capacity (e.g. 10g) or an Etherchannel uplink.
That aside, Mark's "quick fix" solution might be tried. Auto QoS makes quite a few configuration changes. The major "gotcha" might be that the auto QoS recognizes your video traffic for what it is and assigns it to a class that gets better resource allocation.
