Implicit Associations

Dear lazyweb,

I have a need for software that implements the Implicit Association Test, but I can't find any Free software that fits the bill. So I suppose I will have to write it myself. I am looking for recommendations for which language to use. My criteria are these:

1. I am an amateur coder. I have coded in C, C++, Perl, PHP, Java, Javascript and (ugh!) Visual Basic. I am willing to learn a new language for this project (thinking about Python). However my skillz are somewhat basic, and I have never written a GUI application, which this would have to be.
2. The software needs to be cross-platform (GNU/Linux and Windows XP at least)
3. The functionality I need is as follows: It should display images and text to the user, and record the response latency, i.e. the time between when (a) the image/text is displayed and (b) the user hits a specific key in response. Timing to the millisecond level is needed.

Any and all suggestions will be gratefully received.

Thanks in advance,

John.