If your Skype calls are sounding less than optimal, get some technical detail. In your Skype UI, click over to Tools | Options | Display Technical Call Info. One of the more important stats displayed there is Roundtrip. If this reads 100 milliseconds or more, your call traffic is getting seriously delayed. Try placing the call again, and if that doesn’t solve your problem, it’s time to check your gateway settings.
Tech Stats for Skype Calls