I fixed it, here's how:
I upgraded/restored my phone to 1.1.4
jailbroke with ziphone 2.5
I connected to my iphone wirelessly with winscp
I copied my com.apple.SystemPowerProfileDefaults.plist from /System/Library/SystemConfiguration/PowerManagement.bundle/ to my desktop for editing. I then pasted all of this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>SystemProfileDefaults</key>
<dict>
<key>AC Power</key>
<dict>
<key>Sleep On Power Button</key>
<integer>1</integer>
<key>Automatic Restart On Power Loss</key>
<integer>0</integer>
<key>Disk Sleep Timer</key>
<integer>10</integer>
<key>Display Sleep Timer</key>
<integer>10</integer>
<key>Dynamic Power Step</key>
<integer>1</integer>
<key>Hibernate File</key>
<string>/var/vm/sleepimage</string>
<key>Hibernate Mode</key>
<integer>3</integer>
<key>Reduce Processor Speed</key>
<integer>0</integer>
<key>System Sleep Timer</key>
<integer>10</integer>
<key>Wake On AC Change</key>
<integer>0</integer>
<key>Wake On Clamshell Open</key>
<integer>1</integer>
<key>Wake On LAN</key>
<integer>1</integer>
<key>Wake On Modem Ring</key>
<integer>1</integer>
<key>Display Sleep Uses Dim</key>
<integer>1</integer>
<key>ReduceBrightness</key>
<integer>0</integer>
<key>Mobile Motion Module</key>
<integer>1</integer>
</dict>
<key>Battery Power</key>
<dict>
<key>Sleep On Power Button</key>
<integer>1</integer>
<key>Automatic Restart On Power Loss</key>
<integer>0</integer>
<key>Disk Sleep Timer</key>
<integer>10</integer>
<key>Display Sleep Timer</key>
<integer>10</integer>
<key>Dynamic Power Step</key>
<integer>1</integer>
<key>Hibernate File</key>
<string>/var/vm/sleepimage</string>
<key>Hibernate Mode</key>
<integer>3</integer>
<key>Reduce Processor Speed</key>
<integer>0</integer>
<key>System Sleep Timer</key>
<integer>10</integer>
<key>Wake On AC Change</key>
<integer>0</integer>
<key>Wake On Clamshell Open</key>
<integer>1</integer>
<key>Wake On LAN</key>
<integer>1</integer>
<key>Wake On Modem Ring</key>
<integer>1</integer>
<key>Display Sleep Uses Dim</key>
<integer>1</integer>
<key>ReduceBrightness</key>
<integer>0</integer>
<key>Mobile Motion Module</key>
<integer>1</integer>
</dict>
<key>UPS Power</key>
<dict>
<key>Sleep On Power Button</key>
<integer>1</integer>
<key>Automatic Restart On Power Loss</key>
<integer>0</integer>
<key>Disk Sleep Timer</key>
<integer>10</integer>
<key>Display Sleep Timer</key>
<integer>5</integer>
<key>Dynamic Power Step</key>
<integer>1</integer>
<key>Hibernate File</key>
<string>/var/vm/sleepimage</string>
<key>Hibernate Mode</key>
<integer>3</integer>
<key>Reduce Processor Speed</key>
<integer>0</integer>
<key>System Sleep Timer</key>
<integer>15</integer>
<key>Wake On AC Change</key>
<integer>0</integer>
<key>Wake On Clamshell Open</key>
<integer>1</integer>
<key>Wake On LAN</key>
<integer>0</integer>
<key>Wake On Modem Ring</key>
<integer>0</integer>
<key>Display Sleep Uses Dim</key>
<integer>1</integer>
<key>ReduceBrightness</key>
<integer>1</integer>
<key>Mobile Motion Module</key>
<integer>1</integer>
</dict>
</dict>
</dict>
</plist>
... straight over the top of everything in the file already, and copied it back onto the phone, overwriting the original version. I restarted my phone and everything was working perfectly.