To resolve this issue please try to following steps and see if the issue is resolved after each step:
1. Add "/3GB /USERVA=3030" to the Boot.ini. For more information and detailed steps you can refer to ME823440
2. Run isinteg to fix the logical errors in database. To do so:
(A) Dismount the database.
(B) At the command prompt run the "isinteg -s servername -fix -test alltests" command against the database that is experiencing the problem. To do so follow these steps:
a. At the command prompt change to the Program Files\Exchsrvr\Bin folder.
b. Type isinteg -s servername -fix -test alltests (where servername is the host name of the Exchange 2000 computer) and then press ENTER.
c. Press the number that corresponds to the storage group name that you want to repair and then press ENTER.
d. Press Y to confirm the selection and then press ENTER.
e. Repeat the isinteg command until the number of database fixes reaches 0 (zero) or does not change.
f. Quit the command prompt.
(C) Start Exchange System Manager and then mount the database.