Does your event log give any indication was going on? Tried updating the drivers to your nic? Dunno, but here are a few rips as shots. Good Luck!
Change the setting in Internet Properties/Conenction to Never dial a connection.
in a dos window (cmd.exe)
Type ipconfig /release
Type ipconfig /renew
"Why does my home ADSL line lose its connection whenever I pick up the phone?
First of all, make sure you have placed the filters you were provided in the self-install kit or by the installation tech on every phone, fax, or modem connection on the same line as your DSL connection (except, of course, the DSL modem itself). The simplest thing to do is just plug a filter straight into each wall jack except the one to which your DSL modem is connected. (And if you need to connect a phone or other device to that jack, plug it in to the splitter on the phone side)
If you have all the filters installed, there is another possible issue. You may find that whenever you pick up or put down the phone, the DSL modem loses its connection for a few seconds and has to re-sync (you can see this in interrupted downloads or media streams, as well as by watching the lights on the modem; if it starts blinking amber instead of green, it has lost its connection and is trying to recover it).
This can be caused if there is a Maintenance Test Unit (MTU) on your line. An MTU is a small circuit the phone company can use for remote line testing. They are being phased out because they have been found to interfere with data transmission, but if you experience this sort of problem, you can call the telephone repair hotline at 611 to find out if you have an MTU on your line and to have them remove it."
"Q: I lose line sync regularly (#209)
A: Frequent loss of line sync (the usually green light on your DSL modem goes out, blinks, turns yellow or red, and the Internet is suddenly unreachable) can be because:
You have line noise
Your modem is faulty
Your CO DSLAM has a line card problem
Frequent CO DSLAM upgrades that are not communicated to you.
If the problem is regular - for example, at roughly the same time almost every day and it lasts for some time, you should investigate whether or not local line interference is the root cause. This could be: street lights going on, local transmitting towers of any kind, lights or electrical devices in or around the home that are possibly routed near your inside wiring. Unfortuntately, having guessed this is the cause, it is often very hard to correct.. even another copper line might have the same problem.
If you suspect modem malfunction, check for heat, replace the modem if you can, if it is an internal modem, change slots and try running with minimum other internal cards (remove SCSI cards, soundblaster cards and so on), to verify the root cause is not a plain old windows hardware conflict problem.
If all else fails, it may be a marginal card in the CO DSLAM, that is causing your line problems. Suggest (although this might be ignored) that the DSLAM card get re-seated, or you are swapped to another card."