This issue can occur due to the presence of Cisco bug ID CSCeh84289.
For a workaround:
Refer to Cisco Downloads in order to download and install any of these FWSM software version or the latest versions:
Refer to Managing Software and Configuration Files for more information on the upgrade procedure, license management and so forth.
Use the TAC Service Request Tool in order to open a case with Cisco Technical Support for more assistance with this issue.