Question about MS ISA 2000 on Windows2K3 Ent edition?

Hi,

MS ISA 2000 is asking for authentication frequently from clients and problem gets resolved once pubilc dns removed, flush dns and register dns and adding the public dns back again.
Server is having Win2k3 Ent edition with 2 NICS teamed together.
Has anybody has solution for this issue?

Regds
VVKS