Running a PIC16F628a on 3 Volt Power Supply

I have a PIC16F628a that I want to run off a 3 Volt supply (3V 2032 lithium battery). The PIC works as expected at 5 Volts supply, but when I drop the supply below 4.5 Volts the PIC stops working. The data sheets say this PIC should operate on as low as 2.0 Volts DC supply.

Is there something I am missing??

Help!

Thanks, Russ

Have a read of page 136 and onwards of the data sheet for this part,this may be your issue.

Hope it helps Sphere.

I have a 16f628a running at 3v also and it works fine.(2 AA batteries) As the datasheets show, they wont run above 4Mhz if run at lower voltages. If your trying to run it on a 20Mhz crystal, that may be your problem.

Thanks all, it appears the Brown-Out was enabled preventing operation below 4.3VDC.

Turned it off per Darrel's suggestion and "presto" all is fine!
But good points on the max frequency based on voltage. Good to keep in mind. Fortunately I am running at 4MHz. :-)