The /write bug has already been reported in two versions and Khaled has not fixed it.
/fwrite would be useful if it had all the right switches, but with certain scripts /fwrite is useless.
I hope Khaled fixes the problem. I have been told by coders that it is just a matter of the command he is using for the process.
To prevent this from happening I shut mIRC every 24 hours and restart. It happens after so many writes, as the link says.