Message Light flashing continously

You have unheard messages on the voicemail system provided by your telephone company. This system records messages when someone calls while you're already on the phone.

Please contact your telephone company for instructions on accessing their voicemail system.

Hi
When your red light is on with the handest down presss the message key. this will tell you where the message has come from. I expect you will see that an internal extension has dialled you by mistake. It is a message waiting function on the system for user to call back on. Nothing to worry about. To clear the light you have 2 options either press the clear button on the display for each message or dial *700(then your extension number)

Speak Soon

Phil

Resetting the voice message waiting indicator
When you receive a new voice mail message, the new message LED on the top of the handset flashes. In the event your message waiting light gets out of sync with your phone company's
voice messaging system, you can manually reset it back to the "No messages waiting" state.
1. Press and hold FiND on the base for five seconds.
Note: The handsets connected to the base will start to beep, however, keep pressing for five seconds.
2. A beep sounds and the message alert tone is reset.
Changing the dial mode
Your phone can communicate with the telephone network in two different ways: tone dialing or pulse dialing. These days, most base networks use a method called tone dialing, so your phone comes programmed for tone dialing. If your phone company uses pulse dialing, you will need to change your phone's dial mode. If you don't get a dial tone or can't connect to the telephone network, please follow the steps below to modify your phone's settings:
1. Press MENU/SELECT.
2. Select the Global Setup menu, and then the Dial Mode submenu.
3. Scroll to highlight Pulse.
4. Press MENU/SELECT. You will hear a confirmation tone.
If you ever need to change the dial mode back to tone dialing, follow the same procedure, but select Tone in step 3.

Finally for future ease of use, here is a link to the user manual were I copied the above information from:

http://www.uniden.com/content/ebiz/uniden/resources/ownersmanuals/DECT1580-3om.pdf

You have unheard messages on the voicemail system provided by your telephone company. This system takes messages when someone calls while you're already on the phone. Please contact your telephone company for instructions on accessing their voicemail system.

That is the message waiting indicator, it is telling you that your Call Notes (Or whatever your service provider calls it's voicemail) has a message waiting. If you do not have a message waiting, you can turn the light of by following these steps:

Resetting the voice message waiting indicator
When you receive a new voice mail message, the new message LED on the top of the handset flashes and
appears in the handset display. In the event your message waiting light gets out of sync with your phone company’s
voice messaging system, you can manually reset it back to the “No messages waiting” state.
Press and hold FIND on the base for five seconds.
Note: The handsets connected to the base will start to beep, however, keep pressing for five seconds.
A beep sounds and the message alert tone is reset.

Our just started to do the same thing. Drove us crazy because there were no messages. I couldn't find the manual so I looked up the manual on their website. Here's how to fix it....IT WORKS! With the phone in "stand by", open the menu and select Global Setup.Select VMWI reset. Then select yes.

The red blinking light is an 'event' light, it does not necessarily mean a message is waiting for you, it will also start to flash if you have a missed call.
click 'up' on the round button to show the missed calls list and it will stop flashing, at least it does on mine!

Press down the "find handset" button until the paging beep stops (about 5 seconds) and this will reset the indicator lights on the handsets.

This sounds like you have a call back message active on your phone, The callback is a through back to the days before we had Voice-mail, if you wanted a person to call you back you could activate their message light by pressing your message key while the called phone was ringing. To remove the light you would lift your handset and press the message key then select which party you wished to "callback", once the call was answered at the other end the light would be extinguished. Give this a try, I bet you will be surprised at the results.