Symptom: After installing iTunes 10.5.x upgrade, APSDaemon and Apple Mobile Services take 100% CPU
APSDaemon.exe (otherwise known as Apple Push) is the service that wirelessly syncs your device (part of the iCloud package). Searching through the forums it appears that the most referred to solution is;
netsh winsock reset
This does have a proviso that any software with a LSP will then break;
“Warning Programs that access or monitor the Internet such as antivirus, firewall, or proxy clients may be negatively affected when you run the netsh winsock reset command. If you have a program that no longer functions correctly after you use this resolution, reinstall the program to restore functionality.” 
Whenever you have ANY software on your machine that integrates itself with winsock that adds its own LSP (Layered Service Provider), iTunes 10.5 will break. Antivirus/Antispyware programs will often do this to enable the monitoring incoming and outgoing traffic. In short it appears that iTunes 10.5.x DOES NOT PLAY WELL with any winsock configuration that is not the default. This is an iTunes 10.5.x bug that Apple need to pull their finger out and fix ASAP!
To be honest, I am not going to negatively impact my firewall/antivirus/other because Apple can’t follow the winsock programming style guide. You can also get a good outcome by killing off the APSDaemon.exe – it may safely be stopped from running at startup, but you may not be able to wirelessly sync your device.
My recommendations are currently – remove APSDaemon.exe from the startup items, if/when it starts with iTunes kill the process via Windows Task Manager (
or drop its run priority via “Set Priority > Low” ).
Last updated: 2012-Jan-30 04:49PM GMT+11
Update: 2012-Mar-13 11:00 GMT+11
With 5 days of testing under the belt, iTunes 10.6 appears to fix this issue 🙂
 itunes is using 100 % CPU [Apple Support Communities]
 APSDaemon.exe uses excessive CPU resources [Apple Support Communities]
 apple mobile device service high cpu usage [Apple Support Communities]
 Solution: iTunes 10.5 using 100% CPU / Not backing up your iPhone. [Apple Support Communities]
 How to determine and to recover from Winsock2 corruption in Windows Server 2003, in Windows XP, and in Windows Vista KB811259 (2011-Sep-23) [Microsoft]
 Repair/Reset Winsock settings (Links) [Ramesh Srinivasan]
 iTunes 10.5 for Windows: May see performance issues and blank iTunes Store TS4123 [Apple Support]