If Act! crashes when you attach a document, you may have some Windows updates applied that confused Act!.

Act! v16 supports .NET 4.0 and .NET 4.5.  If .NET 4.6.x is installed, you need to do the one of the following:

Option 1

  1. Uninstall Act!
  2. Uninstall Microsoft .NET Framework 4.6.1, and here is a video on how to find your list of programs.
  3. Re-Install .NET 4.52, which is found here.
  4. Install Act!

Option 2

v16 (Premium): Upgrade all the v16 workstations to v16.3 Hot Fix 1, and here is the download link.

v17 (Premium): Upgrade all the workstations to v17.2 SP 2 (US) and Hot Fix 2.
v17 (Pro): Upgrade to v17.2 SP2 (US) and Hot Fix 2.

Take note: If you upgrade one PC using option 2; then, all PCs + server need to have that same version.

Here is the article from Swiftpage, citing additional details.

Now, this scenario assumes no other programs on this workstation require .NET 4.6.1.  So, you will have to test other programs.  If you fear trying this yourself, we can help.  We have provided Act! tech support since 1997.

The long term solution is to upgrade to Act! v18+. With the advent of Act! subscription, software updates and phone support is included at a reasonable monthly or annual fee.