I'm new to IOS but I'm taking ICND 1 and ICND 2 to catch up. I've gone as far as configuring a 3560 switch from "scratch" in a test environment, and am in part one of ICND 2.
Setting this switch up for HTTP administration, I've been prompted repeatedly for my username and password both when using a browser directly and when using Cisco Network Assistant (currently 5.5). This is different from the production switches I'm working with, that will prompt me once only and let me work. At first I suspected this was because I'm trying to use SSL and an in-house certitficate authority to sign the switch's certificate, but this is happening in plain HTTP as well. If I'm persistent enough, I eventually get the pages or configuration screens I want.
The difference between the production 3560s and my testing one, is the test one uses IOS 12.2(53), the current version. The production ones use 12.2(25)SEE3 through 12.2(35)SE5 and probably everything in between. I'm also experimenting with the releases that includes the web-based device manager on my test switch, but the behaviour is similar whether the image has the web-based manager or not.