The impact is that you will have less capacity for processing on the ISG.
Unfortunately, the syslog message manual has not help on how to troubleshoot this issue.
https://www.juniper.net/techpubs/software/screenos/screenos6.3.0/630_messages.pdf
I would assume this is some kind of hardware failure and if you have a support would open a JTAC case.
If you were looking to clear the error instead, I would try:
restart, if that does not work
Shutdown and reseat the card
But opening a ticket while the issue is in effect will let JTAC gather data or verify an issue for RMA.