HELP about a dbspace can't drop.

Hi All: I got a problem about drop dbsapce. I used the tbmonitor to drop the "mainlog" dbspace. But I got a error message as follow: "cannot drop the dbspace/BLOBspace" "ISAM error : bad isam file format" Does anyone can help me to solve this problem? Thanks a lot. Kevin OUR ENVIRONMENT: H/W:IBM RS/6000 O/S:AIX 3.2.5 DB: Informix 5.01 $tbstat -d RSAM Version 5.01.UD1AH -- On-Line -- Up 1 days 14:44:05 -- 9600 Kbytes Dbspaces address number flags fchunk nchunks flags owner name 30011bcc 1 1 1 3 N informix rootdbs 30011bfc 2 1 3 1 N informix mainlog 2 active, 8 total Chunks address chk/dbs offset size free bpages flags pathname 3001124c 1 1 0 25000 50 PO- /usr/informix5.0/system/online.tst 300112e4 2 1 0 7500 1 PO- /usr/informix5.0/system/online2.tst 3001137c 3 2 0 1000 972 PD- /dev/mainlog 30011414 4 1 0 149504 147814 PO- /usr/informix5.0/system/online3.tst 4 active, 8 total