Can't create a new partition using fdisk it says I must delete one first

[Dave Martini 1]

I'm trying to create a new partition on my boot disk but I get an error
that says I must delete one first. I have 4 partitions defined
so far and want to create a 5th. which I would have thought
would be an extended partition since I already have 4.

Can anyone help?

Command (m for help): p

Disk /dev/sda: 73.4 GB, 73407865856 bytes
255 heads, 63 sectors/track, 8924 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sda1   *         1       127   1020096   83  Linux
/dev/sda2           128       382   2048287+  82  Linux swap
/dev/sda3           383      1657  10241437+  83  Linux
/dev/sda4          1658      2266   4891792+  83  Linux

Command (m for help): n
You must delete some partition and add an extended partition first

Command (m for help): v
106960832 unallocated sectors

Dave Martini
LLNL