MacBook Pro mid 2009 sleep problem

Hi, sorry if my post is not as comprehensive as necessary. I just bought my first used Mac yesterday (Saturday) and I just realized a slight problem. When I close the lid for the MacBook to go to sleep, it undergoes an endless cycle of going to sleep then turning back on. I disabled "Wake for Network Access" on the power options and bluetooth. I've done a SMC? restart and pulled out the .com.apple.autowake.plist onto my desktop and re-booted. When I force sleep from the apple menu, the sleep light "breathes" normal though sometimes I still hear the fans going (is this normal?) but when I close my lid, the light will go off as if sleeping, then turn on for several seconds and repeat. I have no USB devices connected or peripherals. I've quit all my running programs, but still the same thing happens. Specs on the MacBook are: MacBook Pro 13-inch Mid 2009, Mac OS X Lion 10.7.2(11C74 but soon to update though) 2.26 GHz Intel Core 2 Duo, 4GB 133 MhZ DDR3, NVIDIA GeForce 9400M 256 MB.

On the console it says:
2/5/12 6:51:10.000 PM kernel: Wake reason: EHC1
2/5/12 6:51:10.000 PM kernel: Previous Sleep Cause: 5
2/5/12 6:51:10.000 PM kernel: USB (EHCI):Port 5 on bus 0x24 connected or disconnected: portSC(0x301402)
2/5/12 6:51:10.000 PM kernel: An Unknown USB Device (Port 5 of Hub at 0x24000000), may have caused a wake by being connected
2/5/12 6:51:11.000 PM kernel: 00000000 00000020 NVEthernet::setLinkStatus - not Active
2/5/12 6:51:13.000 PM kernel: MacAuthEvent en1 Auth result for: 1c:af:f7:cc:fd:e1 No Ack
2/5/12 6:51:14.000 PM kernel: Graphics suppressed 4533 ms
2/5/12 6:51:15.000 PM kernel: MacAuthEvent en1 Auth result for: 1c:af:f7:cc:fd:e1 No Ack
2/5/12 6:51:19.000 PM kernel: hibernate image path: /var/vm/sleepimage
2/5/12 6:51:19.000 PM kernel: sizeof(IOHibernateImageHeader) == 512
2/5/12 6:51:19.000 PM kernel: Opened file /var/vm/sleepimage, size 4294967296, partition base 0x0, maxio 400000 ssd 0
2/5/12 6:51:19.000 PM kernel: hibernate image major 14, minor 0, blocksize 512, pollers 5
2/5/12 6:51:19.000 PM kernel: hibernate_alloc_pages flags 00000000, gobbling 0 pages
2/5/12 6:51:19.000 PM kernel: hibernate_setup(0) took 0 ms
2/5/12 6:51:19.000 PM kernel: 00000000 00000020 NVEthernet::setLinkStatus - not Active
2/5/12 6:51:21.000 PM kernel: hibernate_page_list_setall start 0xffffff806535b000, 0xffffff806602d000
2/5/12 6:51:21.000 PM kernel: hibernate_page_list_setall time: 180 ms
2/5/12 6:51:21.000 PM kernel: pages 520918, wire 78717, act 116772, inact 5838, spec 337, zf 13353, throt 0, could discard act 47095 inact 40909 purgeable 3891 spec 214006
2/5/12 6:51:21.000 PM kernel: hibernate_page_list_setall found pageCount 215017
2/5/12 6:51:21.000 PM kernel: IOHibernatePollerOpen, ml_get_interrupts_enabled 0
2/5/12 6:51:21.000 PM kernel: IOHibernatePollerOpen(0)
2/5/12 6:51:21.000 PM kernel: IOPolledInterface::checkForWork[5] 0xe00002eb
2/5/12 6:51:21.000 PM kernel: PMStats: Hibernate write took 1 ms
2/5/12 6:51:21.000 PM kernel: all time: 1 ms, comp bytes: 0 time: 0 ms 0 Mb/s, crypt bytes: 0 time: 0 ms 0 Mb/s,
2/5/12 6:51:21.000 PM kernel: image 0, uncompressed 0 (0), compressed 0 (0%), sum1 e2da656f, sum2 0
2/5/12 6:51:21.000 PM kernel: wired_pages_encrypted 0, wired_pages_clear 0, dirty_pages_encrypted 0
2/5/12 6:51:21.000 PM kernel: hibernate_write_image done(e00002eb)
2/5/12 6:51:21.000 PM kernel: sleep
2/5/12 6:51:22.000 PM kernel: Wake reason: EHC1
2/5/12 6:51:22.000 PM kernel: Previous Sleep Cause: 5 (repeats)

It mentions hibernate stuff and wake reason: EHC1, port 5, unknown USB device etc. Are there any suggestions or input? If any more information needs to be provided, let me know. Thanks in advance.

I someone over at the Apple Support Forums said this might have something to do with a version of Candelair, is it possible you have this installed?

discussions.apple.com

Thanks for the quick reply. No, I do not have Candelair installed (unless it was previously installed and left some files). iWork/iLife and Microsoft Office came installed with the computer. I installed smcFanControl and Dropbox. I've disabled Dropbox but the problem persists.

It seems the MacBook is turning on and off regardless of a closed lid or not. Upon removing the bottom casing however, the problem disappeared. The MacBook actually slept. Any thoughts?