Gmail error user name or password for Gmail incorrect iPhone

Starting the other day I am getting the above error when I try to access my gmail account on my iphone4 and I get the same error on my iMac. This is the 2nd or maybe 3 time this has happened. The last was exactly month ago.
Also keep in mind I can access gmail directly on the web using the same id and pw that is in iphone and mail app on imac. The last time in Jan I tried deleting and reinstalling my gmail account 4-5 times but with no luck, same error msg and gave up. A couple days later and it just started working again.
Any ideas on what could be causing this and is anyone else having similar issue with gmail?
iMAC Mac OS X (10.6.6)