The below steps describe how to disable a safety feature by removing GFCI protection from your circuit. Check with local codes and verify that the problem isn't simply a bad GFCI or malfunctioning appliance before considering following these steps.

It sounds like your normal outlet is wired to the GFCI, making it a protected outlet.

Turn the power off, and remove the GFCI. You should see Black and White wires connected to the "LINE" Terminals, and another pair Connected to the "LOAD" Terminals. Devices with motors can trip GFCI outlets due to inductive loads at start up or shutdown.

Get yourself some spare wire. If you don't have any, buy a foot of 14/2 household wire from the local Orange or Blue Big Box Store. Also pick up some wire nuts rated for 3 14 ga wires.

You'll need to cut 4-6 inch white and black "jumper" wires and strip the ends.

Disconnect all wires from the GFCI, and screw in the LOAD screws all the way. I like to tape them off with electrical tape.

Attach one end to the LINE Terminals, matching white to white and black to black. (Brass screw is black, Metal screw is white. Green screw is ground (green or bare).

Now wire the three white wires together with a wire nut. Similarly, wire the blacks. These are called Pigtails.

Wire the two remaining ground wires to the ground (green) screw on the GFCI.

Stuff the wires in and re-mount the outlet.

You've just unprotected the fridge and freezer. However, I'd put a label on the unprotected box "NOT GFCI" so that a future owner doesn't make any assumptions.

EDIT: There may be a code requirement to have all garage circuits GFCI protected. Check with your local authority before doing this.

NEC 2008

210.8 Ground-Fault Circuit-Interrupter Protection for Personnel.
(A) Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in (1) through (8) shall have ground-fault circuit-interrupter protection for personnel.

(2) Garages, and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use.

It's true GFCI's do go bad and will wear out over multiple trips. So replacing one after 30 years is a good idea since the replacement is not all that expensive. But lets say the replacement does not fix the problem.

So to start, let's look at how a GFCI works. It is a closed loop system unlike an overcurrent protection. It actually measures the current in the hot wire against the return current in the neutral and if it senses a slight difference. It acknowledges there is leakage in the circuit itself. Since it is not intelligent it can only assume that there is a problem and therefore it trips.

When we troubleshoot a GFCI. WE start by removing all loads attached to the device. Then if we reset the device and check to see if trips. If it does not trip then one or more of the pieces of equipment attached to the circuit has some sort of problem. If it does trip we know that the installed GFCI device and its circuit is the problem and you begin a step by step approach to investigate and locate the problem internal to the circuit itself.

Moisture is a big player in GFCI tripping and you don't need much. For example many times on a construction site after a rain, an extension cord with a very small crack or cut in the jacket, not the insulation, will absorb enough moisture into the fill material of the cord to trip a GFCI. Remove the cord and set it out in the sun to dry for a few hours and you will be able to plug it back in and it will work.

So remove all equipment from the circuit. Check all cordage and exterior devices for moisture and make sure they are in good condition, clean and dry. Pay attention to equipment cordage that is making contact with the earth. More than likely the problem will make itself apparent. Reset the GFCI, if it stays reset then plug each piece of equipment onto the circuit one at a time and check to see which pieces of equipment are tripped your device. Replace or repair any piece of equipment causing a trip.

Hope this helps.