Pete's Packet

http://www.cisco.com/en/US/products/hw/routers/ps259/products_tech_note09186a0080094a0b.shtml

rommon 1 > dir flash:
         File size         Checksum   File name
5358032 bytes (0x51c1d0)   0x7b16    c2600-i-mz.122-10b.bin
rommon 2 >

is the image valid?

rommon 2 > boot flash:c2600-i-mz.122-10b.bin

or

rommon 2 > confreg
correct if necessary (0x2102)

rommon 3 > reset

I had 3 routers crash today! Three different IOS's = bad checksum . What's going on? 

Hmmm a clue; *** System received a SegV exception ***
ERROR: 'Segmentation Violation (SegV) Exceptions' are always related to software
issues.
TRY THIS: Please refer to the TAC Case Collection - SegV exceptions for troubleshooting.
REFERENCE: For more information, see SegV Exceptions.

http://www.ciscotaccc.com/kaidara-advisor/core/showcase?case=K21445274
Cause of SegV Exceptions
SegV exceptions are always software problems. It is possible for different software issues to cause a SegV exception, such as:

 Access to an invalid memory address
 Write access to a read-only memory region
 A jump to an invalid PC (often 0x0)