I have a 2006 HHR with no reverse lock out. I have read replacing the shifter assembly with a 2009 will cure the problem. Will this later shifter work with the cables without problems.

SOURCE: 2002 PT Cruiser Shifter Wont Go Into Reverse - Manual 5 speed

I had the EXACT same problem on my 01 PT. Very easy and inexpensive fix. There is a bushing that is located under the air box under the hood. It is in the shifter linkage. It falls apart from the heat of the engine and age. Mine was completely gone! The dealership didn't sell the bushing itself, they wanted to sell the whole arm for $$! I found this place that sells polyurethane bushing that work great. They sell you two, one for under the hood and one under the console. I just replaced the one under the hood.
All you have to take off is the air box, press the bushing into the sleeve then press it onto the pin and you are done. This place sells them as race parts that gives you a tighter shift.
http://www.boogerracing.com/boogerbushings.html

SOURCE: 2007 HHR gear shifter button engaged and stuck in park

I had the same problem and once I wiggled the shifter enough to get it out of park then the key stuck in the ignition started.

SOURCE: Gear shifter sticking (auto) from Park to reverse and vice versa.

you need to have the shifting cable lubricated or replaced.

SOURCE: car will not shift into gear

Sounds like a linkage/cable to me. Disconnect the linkage at the transmission and move the shift actuator by hand to see if there is the same things happening. Don't try to do this with the engine running unless someone is holding the brake inside the car.

SOURCE: manual transmission will not go into reverse

Behind the battery where the cables connect there is a part called a carrier 1J0711256...less than $35@ vw dealership...easy to install...remove breather...take bottom cable loose...put part on