I think what u need is to see whether u have given the adequate Table space quotas to the users.
Just see the view for ts quotas and give more table space quotas to the particular users. Alternatively , u can allocate a new default table space to the user, with autoextend on and maxextents unlimited. So it wont give error for lack of quotas as it will have unlimited for the user.
Sounds like your quota error is with your OS. Check to make sure that the Oracle software owner doesn't have any restrictions on how much space they can use. Also, check to make sure you have enough free space on F:
Yeap! a low memory could cause this problem. This this message is kind of missleading, I have heard of this problem. Check your event log and see what had happened at the time of failure. That will reveal the secreat to an extent.