Hi ftobe,
The way the charger works is by first fully discharging your battery before reconditioning it. When you get a blinking light in the beginning, it means that your battery is not seated properly in the charger. Make sure that tiny switch for reconditioning mode is fully in the up position and not stuck in the middle. Then replace your battery in the charger making sure it clicks securely. When it is secure you will get a yellow light, and start reconditioning.
If you get a yellow light at first and then after several hours you get a red blinking light, that means your battery has overheated and needs to cool down. When charging your battery in both modes you need to keep an eye on the time. With my new charger, after 2-3 hours of normal mode, the battery needs to be taken out to work. If you leave it in longer than that it will blink red and start discharging your battery to cool it down. With recondition mode, you need to keep an eye on the time too. It should be fine for about 16 hours, but after that if it overheats it will again start the cool down procedure. By the way, after nearly 16 hours of recondition mode with the yellow light to show it is working, you don't need to put it in the charger in regular mode for more than 10 min or so before the light changes from red to green.
In order to help you more I need to know if when you put it in the charger in normal mode you get a red light that is not flashing to begin with and how long before the light starts flashing? Do watch the battery at the 1 hour and 2 hour and 3 hour charge points to see if has gone from red to green or do you just check on it after 4 hours and find it flashing red? For reconditioning mode, do you get a yellow light to begin with and how long before it flashes red?
Also, I need to know what was the condition of the battery before you tried the new charger. Did you get 10 min or playtime or how long? Did the battery overheat causing your Pleo to get sleepy often?