Sorry for the delay in replying. (I've only just seen your post).
The symptom you describe is typical of a poor download speed to your router. Run a ping test here:
http://www.pingtest.net/
If you don't get an 'A' or 'B' result, you need to get your phone line checked.
Then run a speed test here:
http://www.speedtest.net/
You theoretically need at least 1Mbps download speed for internet radio, but I'd suggest that 2Mbps would provide greater reliability. Remember that the speed you achieve will probably vary according to the time of day. Some ISPs have a very high 'contention ratio'. (That indicates how many other users you're effectively sharing your broadband connection with). Most are around 30 to 1. Some are as high as 50 to 1. You really need a contention ration of no worse than 20 to 1 but the 'bargain basement' ISPs won't give you that. (My ISP has a contention ratio of 7 to 1 but I pay 'business prices' for the privilege).
ISPs also have their own 'traffic management' protocols. That means that they deliberately slow some types of internet traffic, at certain times of the day, in order to try to share out limited capacity at peak times. If your download speed is inadequate, speak to your ISP or seek out an alternative ISP with a lower contention ratio.
Chris