youtube videos wont play in browser on sony ericsson xperia x10 mini pro? what

[mAyesha™mmm]

could the problem be? i click on the thumbnail but i doesnt respond .. the videos dont play.. even shorter videos like a minute long. i've had the mobile for one year and a half..It was never like that before.just recently this has started to happen.
has anyone else faced this problem? what can i do to get rid of this on my mobile?

thanks.. much appreciated