Lost member password

Occasionally, some member of my forum lost password(can't log in with message wrong password) and I must reset new password for them. I don't know why??? please help me,otherwise, members of my forum will also lost!!!
This is my forum a3cuatoi.forumotion.net

They must be genuinely losing the password.
Or one more reason could be google chrome, it sometimes gives those errors while logging in.

No. It can't be, because each member of my forum used to use only one password for every page that they register. I think the reason for losing password is due to the forum,may be server. So sad!!!

I doubt if thats the case. Provide them new passwords, thats all i could suggest.