Login fields blacked out in Safari 5.0.6

We recently updated our website and are now getting complaints from users running OSX 10.5.8 with Safari 5.0.6 about our login fields. They state that the Login ID and Password the fields turn Black and they are unable to see what they are typing in.

The website is: https://mychart.med.utah.edu/mychart/

No other browsers have this issue and I don't have an old Mac to replicate the problem on. We can't really ask our users to upgrade their OS and browser, so I'm hoping there's something we can add in our css file to force these fields to render correctly. Any ideas?