The account being used for installation is important. During the installation, the process will deploy or updated dll's and binaries to the operating system at the permission level of that user. So checking these items on the checklist should help to prevent any issues while updating or installing Nintex products.
1: Check that the UAC setting for the account used is temporarily turned down. (You will need to do this on each server that makes up the SharePoint deployment excluding Exchange and SQL.) (Microsoft Reference)
2: Check that on-access scanning is turned off temporarily for SharePoint servers. There are many flavors of anti-virus, some impact and some don't on the installation process. To rule it out, temporarily disable it.
3: Check that the account has Farm Administrator and Local Machine Admin rights. This account will need local admin rights for all the hosts
4: The account will need SQL read/write access at the point you click update. In the background, it will be updating the Nintex databases under the context of this user, that you are logged in as.