Invalid Blob length??

I used delphi3.0 and Sql server6.5 for my c/s application.
I had a sql server field ,it is a image field field,i used to save
my client photo.
but i only save small size photo to this field,<=700k bytes size.
when i save a 1M bytes size photo to this field,BDE tell me:
"Invalid BLOb length.."
what can i do to solve? thank u a lot !!