According to one of my site admins, in the latest versions of aMember the search behaviour has changed. In previous versions if you typed an IP in to the search box it would bring up all records of anyone that has either signed up with or logged on using a particular IP address. Now it no longer seems to search the access logs, it only locates people that signed up with a particular IP. This is not very useful, as we're more interested in the access logs. Could this be reverted back to its previous behaviour?
Nothing was changed in this part. User search always look up registration IP. I think you did some customization to achieve your needs that was overwritten with upgrade. Feel free to add this feature to our bugtracker http://bt.amember.com/. We consider to implement it in core. Best Regards.