portal doesn't divide any space?

[akmassassin]

k heres a little problem that i had just after creating my exactportals (my map is all doned) :

### WARNING: portal doesn't divide any space (it may be coincident with seam sealer?). [see green in error geometry]
EAX: 0xFFFFFFFE
EBX: 0x00000001
ECX: 0x00121D18
EDX: 0x00000000
EDI: 0x00121D18
ESI: 0x00000000
EBP: 0x00121FF4
ESP: 0x00121BE4
EIP: 0x7FFE0304, C3 9C 81 0C ?????
EXCEPTION halt in \halopc\haloce\source\tag_files\tag_groups.c,#3157: #512 is not a valid structure_bsp_cluster_portal_block index in [#0,#512)

is it because there is a problem in the sealing of my exactportals??? please help if you know wat is the prob... thx