If there is a thread on this plz just point me in the right direction

Allmost a year of using TeamSpeak and this is a new one for me.

User A can be heard by some but not all users. We thought it was an East Coast/West Coast problem (hes East, users who cant hear him are West) but that doesnt hold true. I am East Coast as well and can hear him every time loud and clear as can a few of our West Coast users. Some ppl just cant hear him no matter what settings we change for him. One user finally said she could hear him but that changed the next day.

Hes running W2k connecting to our 28.40 ver of TS with onboard sound card (I think).

Any ideas or other info needed?