Some of things to try 1. JRE was upgraded. The newer JREs from Oracle dont play well with IPS. Do downgrade to something compatible. JRE 1.5_10 / 1.6_03 which worked well for me in the past
or 2. The cache for compiled sigs is corrupted. When this happens the virtual sensor vs0 instance does not comeup (IPS is stuck in this state of trying to bring up the sensor and hence unresponsive). To check form the CLI prompt run either 'ipslog' or 'show sensor statistics'. Forgot the exact wordings but something to the effect of 'busy compiling ...' and remains in this state for more than say 15-20 mins then you have run into this issue. When this happens one either drops into the linux prompt using the 'service' user class id that you create to get to the $ prompt and erase the cache. Yes this needs blessings from the Cisco TAC gods :-). If its not a production machine but a lab machine you can try reimaging the device on the startup boot prompt #3 (First is normal boot, 2nd is reset pass and 3rd is Rescue Mode / Reimage). OR 3. Sometimes its just a transient flakiness in the TCP stack on the IPS. To get it back to sane state. Instead of pinging from Test PC to IPS , ping from IPS to Test PC. Once you see a successfull ping usually things work from then on. - R. Shenai
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