@ Giraffe,
Your signature indicates that you are using Avast 4.8, yet the latest build is 5.0.594. What version are you using?
Besides Comodo FW, what other programs are loading on start up? Are any of them essential? Can you delete or delay the non-essential ones to speed up your start up?
I would also suggest cleaning your cache, temp. internet files, etc. with something like
CCleaner http://www.filehippo.com/download_ccleaner/ - it is a freeware system optimization, privacy and cleaning tool. It removes unused files (cache, temporary Internet files, etc.) from your system - allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. Additionally it contains a fully featured registry cleaner. Many of us use it here.
As you read in Vlk's thread, the shields of Avast do start up in sequence, and the next release will improve the speed of this, but please take a look at your start up programs. Question: Did this longer delay occur after installing Comodo?