I recently ran into this problem as well with one of our employees at work. I was able to find a solution but I'm not sure if it was the best and only solution to the problem. This problem was only affecting this one person's ability to browse the internet (via IE7 on WinXP Pro) when he logs on to any machine on the network. Kept receiving the security warning popup window dealing with a file called navcanl from ieframe.dll. Other users were able to log on this machine and browse the internet just fine. No matter what machine he logged onto he would receive this error so I'm thinking the problem was tied to user privileges. I think this problem started after a Windows Update just like others have noted.

First, I disable all of his addons (he had about 10 - 12 of them on his profile...others had about 8 or 9). I restarted IE7 but that didn't seem to make much of a difference because it still had the problem. I went to user accounts and noticed that his user name, domain, and group and was somehow missing from the list when I know for a fact that his account used to be listed there along with the other accounts. I didn't think much of it but I went back and added his account again as well as give him power user privileges and then logged him off. After logging him back on he was now able to browse the web again without getting the navcanl/ieframe.dll error message. I went to the other computer that he was having problems with and re-added his account there as well and then logged off and back on again and the problem was fixed there as well. I don't think the problem was with his IE7 add-ons because I re-enabled them prior to adding user privileges.

Hopefully this info helps others as well.