Mouse will not charge -Keeps flashing red light

Here's a guide;
What do the battery lights mean on my mouse? Some keyboard and mouse models feature a battery light that shows the current status of the batteries. The following table describes the different lights and states.
Light
Device Model Status Single long green blink Rechargeable Batteries are good. This occurs when batteries are first installed or every time that the device is turned on. Slow green blink Rechargeable Device is docked in the charging station and is charging properly. Steady green Rechargeable Device is docked in the charging station and does not need additional charging. Steady green Presenter Mouse (Japanese version) Laser pointer is on. Red/green blink Wireless Device is discoverable (trying to connect to the transceiver). Slow red blink Non-rechargeable Batteries are low and need to be replaced. Slow red blink Rechargeable Batteries are low and need recharging. Fast red blink Rechargeable Device is docked in the charging station, but there is a charging error.
Reasons for errors: The wrong type of battery is installed; the battery or batteries are missing; or the battery connection is bad.
Solutions: Make sure that the correct battery or batteries are installed, and are installed correctly. If necessary, remove the batteries, wipe them with a clean cloth, and reinsert them. Steady red Presenter Mouse (Standard version) Laser pointer is on.

I had the same issue -- charged it for days and still red light flashing. I was ready to break it open and see if I could replace battery. Then I looked on the opposite end of the charger and seen a little round hole thingy. I put the end of a pen in there and pushed it twice and -- the red light went away . Plugged the charge in and steady red then purple and now blue. Looks like that is a reset ..Try it -- it worked for mine.

so it works but is flashing red i suggest you try this unplug it for a few hours and then plug it back in if that does not work then your mouse is getting ready to die so go out and by a new one

Flisging red light: Your batteries need replacing.

I still have the manual for my mouse.  Model number 64321.
When this mouse was manufactured it used NiCad batteries which developed a memory much more than the newer batteries.  The older NiCad batteries needed to be conditioned occasionally so Kensington provided a way to do that with the charging base. 
The red light is for indicating discharge status of NiCad batteries.
The red light will flash quickly when you press the battery discharge button on the bottom of the base.  This indicates that you now have 5 seconds to place the mouse in the charging base for battery discharge.
The red light will flash flash more slowly when the battery is being discharged.
After the battery is fully discharged, the base will then charge the batteries.
It should be noted that very few manufacturers of products that utilized NiCad batteries provided a "battery conditioning" feature.  Kensington was unique in this regard.  Battery conditioning allowed NiCad batteries to have a longer useful life.

Now maybe you can help me....  I lost my power supply that plugs into the USB connector.  If you have yours, can you tell me what the output voltage is and what the polarity is of the inner pin.  This will be marked right on the power supply base.  
I plan to just get a generic power supply from Radio Shack, but I need the voltage value and polarity.  Until then, I can still use the mouse, but it won't charge.  FOr now, I'm just using standard AAA batteries.
Thanks.
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Most wireless mice will hibernate after a short period of inactivity. If something bumps the desk or moves the mouse it will start scanning again. If you don't like the light, you could try a laser mouse (no red LED flashing).

Now what you have to do is look for a reset button on your mouse and your wireless mouse signal receiver.
When the receiver and mouse both are on press the reset button on both of them one by one.
This should solve the problem.

You need to tell us more then "MY mouse"... but I'll try to help.
First: there must be button to power off/on your mouse, switch to off and then on. If red light continues to flash clean connections on mouse and on dock (where you charge mouse), try to charge it, if red light continues to flash check if you can replace battery if not it's time for new mouse.

I found the following:

Red light slow blinking: Battery Low, please put mouse in charger and charge;

When in Charger Red light Slow Blinking: No charging, please check and clean Gold Plated contacts in charger and Mouse;

When in Charger green light Blinking: Charging in progress

When in Charger green light Steady: Charging complete

When in Charger Red light Fast Blinking: Mouse detects overvoltage during charging! Please clean Battery contact inside Mouse, or replace rechargable batteries NiMh 1500-2100 mAh only

cycle the batteries in a external charger a fex times (charge then discharge) I suspect that over the years of using then putting it in its dock the batteries have had a very erratic charge discharge cycle cycling them as I suggest should bring them back.