I had major issues updating to the new Hopkinton update, my a/v kept flagging the startscreen.exe as malware, which in term kept corrupting the update.  I managed to fix it in the end by flagging it as an exception.  However, I thought I'd bring this up as other people may be getting this issue as well.
 
For information, I purchased through Steam, am running Windows 10 and am using 360 Total Security (free edition) as my a/v.

FYI Quihoo 360 is a very, very bad AV program. I would highly recommend you find something else. Avast is a good choice for free.

Before I got the paid version of Webroot's SecureAnywhere (which is fantastic), I've had great experiences with Microsoft's Security Essentials (free): http://windows.microsoft.com/en-us/windows/security-essentials-download

still, strange that the start screen is a separate exe?

kevmsmith81
I had major issues updating to the new Hopkinton update, my a/v kept flagging the startscreen.exe as malware, which in term kept corrupting the update.  I managed to fix it in the end by flagging it as an exception.  However, I thought I'd bring this up as other people may be getting this issue as well.
 
For information, I purchased through Steam, am running Windows 10 and am using 360 Total Security (free edition) as my a/v.

I suggest you email 360 total security and tell them. Then dump it in favour of AVG and Malwarebytes :)

I had installed 360 on the basis of some reviews.  However, I've read some more and decided to go with Avast instead.

There is a difference between general antivirus software and software that also does internet security/firewall types of things.  Looks like this package does both so the flag may not be as malware per se but as an app that is accessing the internet and is not known yet by the security suite.
 
FWIW, Virus Total ran 54 AV clients (including several well known ones) against our start screen and didn't detect anything.

FYI, Avast had issues with X3 installs, threads about it found on Google using search string:
site:forum.cakewalk.com avast x3 install
I have not read anything about issues with the new SONAR.

I've used Avast for about 5 years, now, and it wasn't a problem for me with X3. I'm surprised to hear some were having problems with it and their X3 install. I think it's a great choice for an A/V program (the free or premium version). I also installed SONAR Platinum without any issues from Avast. And my thanks to Cakewalk for the extended trial of SONAR Platinum!
 
Microsoft Security Essentials can't be installed on Windows 10. Windows Defender was converted into Security Essentials, in Windows 10. Moreover, when another A/V besides Windows Defender is installed in Windows 10, Windows Defender is automatically turned-off.

Keith Albright [Cakewalk]
There is a difference between general antivirus software and software that also does internet security/firewall types of things.  Looks like this package does both so the flag may not be as malware per se but as an app that is accessing the internet and is not known yet by the security suite.
 
FWIW, Virus Total ran 54 AV clients (including several well known ones) against our start screen and didn't detect anything.

+1
A program that visits an unknown (to the firewall) website, downloads code and automatically installs it might well look like something nasty to a robot.