I don't think you have an IDS-4210 sensor.
The IDS-4210 sensor is a 1 Rack Unit sensor with a blue front.
Both NICs of the sensor are built into the main motherboard.
Side Note: the IDS-4210 requires a memmory upgrade to support the newer 4.1 code. The memmory uprade is free for customers with SmartNet contracts.
It sounds like you are referring to the older IDS-4220 or IDS-4230 sensors or the even older NRS-xx sensors.
All of these sensors were 4 Rack Unit sensors with a grey front that required a key to access the front panel. One interface was on the main motherboard and one interface in a PCI slot.
The older NRS-xx sensors had PII400 cpus with less memmory and are not supported with version 4.0.
NOTE: Version 3.1 signature updates are continuing to the first part of next year for these sensors.
If you are running the old NRS-xx sensor please contact your Cisco Representative about upgrading to a newer sensor for when the 3.1 signature updates stop.
The IDS-4220 and IDS-4230 sensors have PIII600 cpus with more memmory and do support version 4.0.
NOTE: The IDS-4220 like the IDS-4210 requires a memmory upgrade to support version 4.1. The memmory upgrade is free for customers with SmartNet contract.
From the description of your problem I would have to guess that you have an older NRS-xx sensor that does not support version 4.x.
Reboot the sensor and see what CPU is reported on the screen just before bootup of the operating system.