Sounds like you may have an IRQ Conflict...with your DSL you need an NIC and the NIC is what is considered a "high speed" device, so is the sound card or video card. Sometimes Windows will allot them the same IRQ number and due to this sharing of incompatible devices it causes a conflict causing one or the other of the devices not to work at all or not to work properly.
If you have a windows based system, click on start>programs>accessories>system tools>system information> expand the list under "hardware" and highlight "conflicts/sharing".
This will show you any devices sharing IRQ numbers. If they happen to be in conflict you can manually adjust the IRQ or if you are not comfortable then take it to someone and have it done.