Right now here seems to be a problem installing new over the existing version. I suggest that Avast make the new version automatically uninstall the old version before installing new one. That would save a lot of people that may not be computer literate from problems. Other software does this.
Joe
So, which problem do you have…??
asyn
I don’t have a problem I just see an abnormal amount of problems with this release. A lot of software automatically uninstalls the old version before installing the new to prevent problems. The first thing recommended to people having problems with this version that installed over an old version is to uninstall and reinstall.
Joe
Usually, it’s perfectly alright to install over the old version…!!!
Even, if you install over the old 4.8 version. 
asyn
Apparently it’s not working well this time. You rarely see this many posts about problems with an update.
Joe
This is a big update (considering it is only meant to be a .1 update from 5.0) and it really isn’t a lot of posts when you consider the avast user base and I have been active in the forums for almost 7 years.
The problem with an auto uninstall if you update from the GUI or you install over the top you lose all your customizations and exclusions, etc. and I would suggest that you would find more people squealing about that.