os x lion Reinstall problems

HI

I am having trouble reinstalling lion on my late 2006 imac. intel 2/0 ghz machine.

i was going to sell the device and did a drive cleaning and reinstalled the original version of tiger that it shipped with.

after all of that the screen developed the dreaded verticle line issue.

since i can't sell if for much now i decided to give it to my son.

i upgraded to snow leopard again with no trouble and then wanted to put lion back.

i went to the app store and went to my recent purchases. clicked the re install button for lion and waited.

the download failed. and i was stuck with a dock icon for lion that said downloading was paused.

lion is no longer showing in my recent purchases in tha app store.

i could not resume the down load in the dock, and when i restarted the computer that icon was gone.

the only option i see now in the app store is to buy it again.

how can i get this to re install?