Pre-releases only have a small window of support. The bug report section is closed after the corresponding final version is released. This was also the case when we were doing alpha, beta, RC etc.
I suggest you upgrade to 1.4 final and see if you can reproduce. If you can then start a thread here.
OK, thanks. It was one of those things that was quite strange and random and which I haven't seen before, so it could have been a bug introduced by 1.4 pr or it could have been a hardware/driver glitch and might not happen again or for ages.