2007 Lotus Exige S
I have a similar issue with my Exige when it is cold, probably not your issue though. When I pull up on the reverse lockout ring something connected to that under the boot disengages and drops down, I can actually hear it if I listen close enough. Then I have to push down the reverse lockout ring and I pull up on something covered by the boot with the reverse lockout ring and it will allow me to move the shifter over to select reverse. Hard to tell from your description if your issue is similar or if you simply cannot engage reverse on the transmission side.