> Yes! the programmer was using IB Manager. We couldn't use that table
> updating the blobs fields to a empty string, even rebooting the
> server. We had to drop the table and recreate it.

I did some tests with a sample database provided by Jonathan. IB
Manager (aka Quickdesk) sets the blob ID to 0, but does not set a null
flag of that field (which does not happen if they use "UPDATE my_table
SET blob_field = NULL WHERE CURRENT OF my_cursor").

I checked engine sources whether blob ID 0 is valid. ID of the blob
that is being read from the valid database cannot be 0x00000000. First
4 bytes (in whatever endian) are relation ID and cannot be 0x0000.
This means that Quickdesk corrupts database by setting the blob ID to
0 and not setting the null flag (XSQLVAR.sqlind field).

I do not know what component set they use and if this is a bug in
Quickdesk or component set, but you can try to report them about this bug.

Best regards,
Roman Rokytskyy