I experienced the same symptoms as all of the above after installing the latest 2013 version of AVG Free on a Windows 7 32bit machine.
AVG was the last thing I suspected would be the cause. My computer would hang after starting windows and there would be a blue spinning circle over the network icon in the task bar. CTL+ALT+DEL would not work and nothing else was clickable.
After performing a clean boot and disabling all the startup items and services and then re-enabling them a couple at a time I narrowed the culprit down to AVG. AVG was then uninstalled and the problem was gone.
I too have had the computer lock up on boot. I have 3 computers running windows 7.
All three are doing the same, the desktop will appear, but the AVG 2013 icon is NOT in the task bar. If I click on a icon to open the computer will lock up. I have to push reset button to restart, the task manager will not open. AVG 2013 has also made my internet connection very slow. Have had a lot of hang up and just not working problems. No error codes have appeared. AVG 2013 is just not working with windows 7. I removed it from all 3 computers and installed AVG 2012, Now all is working very well. I also have one computer that is running Windows xp. AVG 2013 is running with no problems at all on this one. Looks like if you have windows xp you can use AVG 2013. However if your using windows 7 you CANNOT use AVG 2013. I have no experience how AVG 2013 runs on Vista.
I have had a similar problem with the 30-day free trial of AVG 2013 2667 on a Windows Vista (Premium Home 32-bit SP2) system. The computer would not boot at all in Normal Mode.
So glad I did the 30-day trial before purchasing a subscription! Needless to say, AVG will not be getting my money.
My solution was to uninstall AVG and find a better anti-virus program.
Note: I had to boot to Safe Mode, rename the AVG files, boot to Normal Mode, restore to original AVG names, then uninstall AVG through Windows Programs and Features.
I've also been having this problem and have had to reboot mulitable time to get after updating to this latest version to get my PC (vista PC) to boot without freezing. Also had the UI completely freeze at times while running a scan which then makes using a PC impossible and cant close the locked program via task manager and then PC just become unable to do anything without a hard reset.
I've seen quite a lot of people say they have the same problem which suggests a rushed and not fully tested version of AVG and this issue is the worst I've had.
There were a few issues with AVG2012 freezing in the past as well and failing to load which I had to go though and uninstal and manually remove everything from the registry before reinstalling to get working again and after uninstalling AVG2013 there is a lot more in the registry then previous versions of AVG to manually remove.
I've gone from being a happy customer who couldn't recommend you enough to not poking you with a super long stick.
Also the Win8 style UI makes the overall look and feel of the UI look ugly and childish.