speed warning

Check your custom poi files.See if you have any with the name having a number in it.For example Super 8 or personal custom poi files you may have put number in the title.That will trigger a alarm.Not aware of any Garmins that alarms when you go over the speed limit.For some models the speed limit sign changes color when you exceed the speed limit has been reported from some members.Not sure about your model.Updates coming out may included this for other models.Will just have to wait and see about that.

I had the same problem with a 350, it turned out to be a alert for Walmarts. The bar would come up on the top of the screen and say "Speed Camera"
It would always happen near a Walmart. I had to delete the file and reload it without a proximity alert. Never happened again.

I looked at your manual
http://www8.garmin.com/support/userManual.jsp?market=4&subca...
and did not find anything that would give an alert for speed.

Please clarify if the "alert" is active all the time. That likely means, as suggested above, that you have some POI file which has a "number" in the file name. We might narrow that down if we knew at what speed the alert sounds.

The alert I mean is a loud dong..Like a warning light on your dash, that's what I thought it was.....The second time it went off I figured it out....

Any messages on the screen? These do point a finger at the area to check.

Just run poiloader but use manual mode.Each time a file comes up hit next not skip.The file with the alert will be very easy to spot.It will have the alert information showing as for distance or speed.