when i try to sign a document in acrobat; on choosing "look for newly inserted hardware tokens" i get a message
"ACROBAT COULD NOT FIND ANY NEW DIGITAL ID'S. IF YOUR DIGITAL ID IS ON A HARDWARE TOKEN, PLEASE MAKE SURE IT IS PLUGGED IN AND THE TOKEN INTERFACE IS PROPERLY CONFIGURED. CONTACT YOUR SYSTEM ADMINISTRATOR FOR FURTHER ASSISTANCE."

i have tried on two machines. kindly help.

It seems like that you had not install PKI RTE
3.65 or 4.0 check that did you had install it or not.
For video demo to install the PKI RTE 3.65 please check the given link:-

http://www.youtube.com/watch?v=M0dVRSPPXmg