I've been having a similar problem on Win 7 64-bit Ultimate, with the system hanging and the desktop icons failing to populate. I had to crash the system with the power button and go through Safe Boot, Chkdsk and the rest of it. This is on a machine with an i7 processor and 12GB of RAM. Avast is a paid-for Internet Security V9.
I've also been getting a number of service timeout errors (7011 etc.), where the services cannot communicate with the Service Control Manager inside the 30ms limits. These happened occasionally, but have now increased in number. I should add that, although I have a number of services and jobs running on startup, all that are not needed are set to Manual or Disabled. Although non-fatal, I don't like to see a new set of errors in the logs when previously they were clean. It seems that the timeout errors are definitely connected with the time and resource that Avast grabs, which then chokes off other services from starting in a timely fashion.
Any unnecessary programs in the Task Scheduler are disabled, with the exception of Avast Emergency Update, which is set to run at Logon i.e. at Startup. I don't know whether this is necessary or desirable, and why it cannot be run at a point after the system is fully up and running. I'll try to find out.
A workaround for the hanging problem seems to be to set Avast services to load after other system services, although this isn't ideal. I'm still getting timeout errors, so I suppose the only way to mitigate these is to edit the Registry to change the ServicesPipeTimeout entry to something more than 30ms. Even so, the bootup is now 3 minutes or so; more than before.
My style of working means that I'm not exceptionally bothered if the system doesn't boot up like lightning, but I do like it to get running properly in due course, without hangs and errors.