I came across an interesting problem today, the MySite link was incorrect, it was working the previous day.
The first step I took was to look at the SSP, which showed that the correct My Site location was entered.
The second step was to look at the Alternative Access Mappings, again they looked OK.
By now I suspected that the ISA server was doing something funny, we had asked the network guys to publish a new rule, so I had a look at the rule settings and found the culprit:
Notice the ‘Apply link translation to this rule’ checkbox, the ISA server was looking at the HTML returned by MOSS and changing the MySite entry, it’s actually a pretty cool feature of ISA that is handy if you are accessing your web application from the internet (to your intranet). But in my case it wasn’t needed and incorrectly setup.
I thought it was an interesting problem, by logically stepping through each potential cause and eliminating it, the root cause was discovered pretty quickly.