When i create a table oracle gives below mention error

Though there is enough space available in the data file of USERS2 tablespace.

I have oracle8i workgroup on windows-NT

datafile status of USERS2 tablespace from enterprise manager
size (M) used(M)
data1.dbf 650 512.932
data2.dbf 500 272.018 <-enough space here
data3.dbf 500 431.406 <-enough space here

create table abc
(acno char(1) )
tablespace users2 storage (initial 1m)

ERROR at line 1:
ORA-01658: unable to create INITIAL extent for segment in tablespace USERS2

What could be the solution of this problem ?????
Thanks in advance.

from Anuj Pathak
Hero Financial Services Ltd.