Is ProWritingAid safe? Why does my anti-virus say it's dangerous?

Norton (and other anti-virus softwares) is notorious for causing issues with Word Add-Ins. Norton relies on a set of heuristics to determine whether something is dangerous. Sadly, one of these is how many times it has seen the same add-in. This is obviously a major issue for smaller software vendors such as ourselves. Norton installs its own plugin to Word that you can't see that in the words of Microsoft "may cause performance issues, the inability to open files within Office, or the inability to install some Office programs."

This Microsoft knowledge base article may help: http://support.microsoft.com/kb/329820

We would recommend that you disable the Norton Office add-in and then try to install the software.

Also if you're interested have a read of this article which may make you think you are wasting your money on Norton. It reveals some of the specious marketing tactics used by vendors of anti-virus software . http://www.codinghorror.com/blog/2007/12/blacklists-dont-work.html