Millisecond Forums

Hi,
I have programmed an experiment in Inquisit on my laptop. In this experiment I have inserted a lot of movies (self-made and of only a few seconds, in .wmv format) within trials. There is no problem with running this experiment at my laptop, but when I run this experiment on a research-computer, there are some flashes at the start of every movie. The movies have a black background, and I want to keep this black background before and after the movie. 
You'll first see a coloured fixation-shape, then you see the movie, and after that there is positive or negative feedback. I discovered that with a white background, the problem of the flashes is gone. But this is very ugly because then the screen switches to white (fixation-shapes and feedback) and black (movie) within one trial. 
Can someone help me fixing this problem, so I can keep the black background but without any flashes in the video? My laptop and the research computer are both Windows. I tried different formats of the movies, but did'nt make any difference. 
My idea was to insert a pretrialpause before every movie (maybe this helps?), but I don't know really how to do that, because the fixationshape is also part of the trial. This is because in one phase of the experiment, the fixationshape is coupled to specific movies, and at another phase of the experiment, the fixationshape is random for every movie. (see below for an example)
driehoek / vierkant = fixationshape
filler_moeilijk_z / 1 =movie

<trial filler_moeilijk_z>
/stimulustimes = [1=driehoek; 1000=filler_moeilijk_z]
/correctresponse = ("z")
/validresponse = ("1", "q", "a", "z")
/ responsetrial = ("z", positieve_feedback)
/ responsetrial = ("q", negatieve_feedback)
/ responsetrial = ("a", negatieve_feedback)
/ responsetrial = ("1", negatieve_feedback)
/pretrialpause = 2000
</trial>

<trial 1>
/stimulustimes = [1=noreplace(driehoek,vierkant); 500=1]
/correctresponse = ("1")
/validresponse = ("1", "q", "a", "z")
/ responsetrial = ("1", positieve_feedback)
/ responsetrial = ("q", negatieve_feedback)
/ responsetrial = ("a", negatieve_feedback)
/ responsetrial = ("z", negatieve_feedback)
/pretrialpause = 1000
</trial>

Besides the idea of inserting a pretrialpause, I would be really happy to hear other suggestions of how to fix this problem.
Thank you!