strange ping behaviour

i have two computers Computer A and Computer B .... bith belong tosame subnet .. my
my problem B cant ping A until and unless A pings B ... when A pings B .. B starts recognizing A and starts pinging ... A has no problem in pinging A at all ... both can ping gateway of the same subnet ... right from the start ....
anyway idea whats happening ???

if you're using NT and the two computers have a very similar name, the Network can mistake the two systems.

go to MS and search for Hotfixes (i think)its covered there. Also search the knowledge base. I can't remember all of it but your problem sounds familiar.
Good Luck!