Need help with acer aspire 5742G!!!?

[bearfrods]

hi im using acer aspire 5742G laptop. when i boot it in normal mode..it says starting windows then it doesnt load to my desktop and instead it displays a black screen... but when i tried using safe mode it boots and loads to my desktop. im using windows 7. this problem has started when i restarted the computer after updating avast antivirus. wht could possibly be the problem? is there anything i can do? thanks in advance.

[GTR]

go in using safemode and do a system restore to a few days ago when it was working?