MacBook screen very dark after resuming on OS X 10.8

MacBook screen very dark after resuming on OS X 10.8

I have a MacBook late 2008 aluminum model (5,1). Occasionally, after reopening my MacBook's lid, the screen doesn't light up. With effort I can see that the password prompt is actually rendered very faintly on the screen.
I tried closing and reopening the lid multiple times and changing the brightness, but no luck. The only way I know of getting out of this is to hold the power button and do a hard reboot.
This started happening after doing a clean reinstall of OS X 10.8. I upgraded very recently from 10.5, where I never encountered this issue.
I'm pasting below the relevant time slice from my system.log (which involved several iterations of closing/reopening the lid) - I didn't notice anything helpful here.
May 19 09:23:29 Christines-MacBook.local loginwindow[51]: ERROR | -[LWScreenLock(Private) screenIsLockedTimeExpired:] | No lock state found, use built in check
May 19 09:23:29 Christines-MacBook.local WindowServer[86]: handle_will_sleep_auth_and_shield_windows: no lock state data
May 19 09:23:29 Christines-MacBook.local WindowServer[86]: Created shield window 0x2e1 for display 0x003f003d
May 19 09:23:29 Christines-MacBook.local WindowServer[86]: handle_will_sleep_auth_and_shield_windows: no lock state data
May 19 09:23:29 Christines-MacBook kernel[0]: Wake reason: EC LID0
May 19 09:23:29 Christines-MacBook kernel[0]: AirPort_Brcm43xx::powerChange: System Wake - Full Wake/ Dark Wake / Maintenance wake
May 19 09:23:29 Christines-MacBook kernel[0]: HID tickle 54 ms
May 19 09:23:29 Christines-MacBook kernel[0]: Previous Sleep Cause: 5
May 19 09:23:29 Christines-MacBook kernel[0]: wlEvent: en1 en1 Link DOWN virtIf = 0
May 19 09:23:29 Christines-MacBook kernel[0]: AirPort: Link Down on en1. Reason 8 (Disassociated because station leaving).
May 19 09:23:29 Christines-MacBook kernel[0]: en1::IO80211Interface::postMessage bssid changed
May 19 09:23:29 Christines-MacBook kernel[0]: en1: 802.11d country code set to 'X0'.
May 19 09:23:29 Christines-MacBook kernel[0]: en1: Supported channels 1 2 3 4 5 6 7 8 9 10 11 36 40 44 48 52 56 60 64 100 104 108 112 116 120 124 128 132 136 140 149 153 157 161 165
May 19 09:23:29 Christines-MacBook kernel[0]: 00000000  00000020  NVEthernet::setLinkStatus - not Active
May 19 09:23:30 Christines-MacBook.local loginwindow[51]: resume called when there was already a timer
May 19 09:23:31 Christines-MacBook.local configd[16]: network changed: v4(en1-:192.168.10.157) DNS- Proxy- SMB
May 19 09:23:32 Christines-MacBook kernel[0]: en1: 802.11d country code set to 'US'.
May 19 09:23:32 Christines-MacBook kernel[0]: en1: Supported channels 1 2 3 4 5 6 7 8 9 10 11 36 40 44 48 52 56 60 64 100 104 108 112 116 120 124 128 132 136 140 149 153 157 161 165
May 19 09:23:32 Christines-MacBook kernel[0]: MacAuthEvent en1   Auth result for: d8:eb:97:b1:1c:9e  MAC AUTH succeeded
May 19 09:23:32 Christines-MacBook kernel[0]: wlEvent: en1 en1 Link UP virtIf = 0
May 19 09:23:32 Christines-MacBook kernel[0]: AirPort: Link Up on en1
May 19 09:23:32 Christines-MacBook kernel[0]: en1: BSSID changed to d8:eb:97:b1:1c:9e
May 19 09:23:32 Christines-MacBook kernel[0]: en1::IO80211Interface::postMessage bssid changed
May 19 09:23:32 Christines-MacBook kernel[0]: AirPort: RSN handshake complete on e