I've just downloaded and installed Houdini Apprentice for Windows. Everything seems to be working properly, except that I can't see the playbar or the time slider on the bottom of the window. (Instead, I just see my desktop through the empty space.) The bar below that seems to be working. I still get the appropriate information from the message bar on the bottom of the window when I run my cursor over where the missing icons should be.
Oops, I forgot to mention that I'm running on Windows XP with 2048 MB of RAM. I have a sinking feeling that this may be insufficient for Houdini, after looking through some of the threads.
This sounds like a graphic card issue. Houdini has some issues with ATI cards, and if you are using NVidia then update your drivers, although I have a 8800GTS NVidia card, and I get the same problem if I use the Beta drivers, so I had to revert back to an older driver.
