Let me explain you the problem as i see it using 3 different browser. I made the test on my site and also on the demo of ProVista here with the exact same results.
There is 2 place where we can see the search box completly on top (this one is correct) and the other place is to the right of New Topic button (this one got problem).
So if i get into Test Forum 1 i will explain now what happened with the different browser with the white search box.
Opera and FireFox:
- Search box is showing completly white when we get there not showing the original text "Search this forum..."
- When i move cursor on the search box i see the original text really quick then the promp to enter the text
- Text is entered and showing in blue while the focus is still on that search box
- Moving focus out of the seach box make the text to disappear completly
Ie7:
- Search box is showing completly white when we get there not showing the original text "Search this forum..."
- When i move cursor on the search box i still see nothing only the prompt
- Text is entered and showing nothing at all while the focus is still on that search box
It's probably a CSS bug since it works correctly if you check prosilver base theme