my iMac late 2009 cannot support 16gb ram

You have the incorrect spec RAM. Correct specs are listed below.

Maximum Memory 16 GB

Memory Slots 4 - 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM

I just upgraded my late 2009 iMac 21.5 " ( 10,2) .

With the existing 2 x 2 GB original RAM , I added Kingston 8 GB( 2x 4 GB- 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM ) .

Installation was a breeze - about 15 minutes .

Now it is = upgraded to 12GB RAM and works great . Also upgraded the OS to X Mountain Lion.

( availble at Amazon for $38 for the kit)

http://www.amazon.com/Kingston-Technology-Notebook-KTA-MB1066K2-8G/dp/B001PS9UKW /ref=cm_cr_pr_product_top

You can also check with OWC if they can trade in your 2 x 2 B RAM's and install four 4GB PC8500 DDR3 1066MHz 204 Pin ones

http://eshop.macsales.com/item/Other%20World%20Computing/8566DDR3S8GP/

You must have the right speed of memory! Anything slower will not work. That is why Apple issuse what speed to use.

Sounds like you are wasting your money on RAM which you clearly know will not work. If you follow the instructions from Apple then you cannot go wrong!