eigrp neighbourship didnt come up in 7200 with dynamips

I was trying to configure a simple eigrp setup with dynamips interconnecting 7200. I used frame-relay interface and put frame-relay switch in between. The address was a class B address subnetted - 172.20.15.0/30 case study in Doyle, volume-I.

The problem was after adding "network 172.20.15.0" under "eigrp 15" on both sides, the neighbourship was not coming up - also route ofcourse! I enabled "debug ip eigrp", nothing came out. Even "sh ip eigrp interface" was not showing frame-relay interface.

I thought it may be due to some dynamips problem and configured one more setup. And problem exist there as well. Now when I enabled debug ip eigrp, as usual nothing came. But when I enabled "debug ip packet" could find that packets (hello packets) are send to 224.0.0.10. But other side on enabling same debugs could find that the packets being dropped saying unroutable packet. So the problem should be "network 172.20.15.0" is not taken effect in one router and but somehow worked in one. I tried configuring and unconfiguring that and it worked.

Now I came back to my original setup where I found the problem initially. I tried unconfiguring and configuring back "network 172.20.15.0". But that didnt help this time. I was completely clueless what was happening. Tried reloading the 7200, no luck. Enabled OSPF on the same interface and I could find ospf is working. So I thought it could be a EIGRP bug in the image. I tried a different image on the same setup. That also didnt help. As a final try I enabled "debug eigrp packets" and tried uncofiguring and configuring "network 172.20.15.0". This time it worked. Also I did the same on other routers enabling debugs. Now everything came up.

But still I dont have a clue why it was not working and how its fixed !!