Can't access via Mapped Netwrok Drive / Ping (Win7 Home)

[finstone]

Dear Helpers,
I just upgrade the Router to TP-Link WR841N and following that, I upgraded to DSM to 4.0.
Right now, my problem is "The DS cannot access as a mapped network drive under windows environment." and I tried to Ping the IP, is also not OK
I had spent 5-6 hours to try out the router setting and service but problem remain. I think I set up wrongly or missed some setting. Please kindly advise me.
Cheers,
Finstone

My Configuration
Environment
DS211J + DSM4.0 + TP-Link WR841N + Dynamic IP (ISP Provider)

DS211J with (Status)
- DSM 4.0 :
- Raid 1 HDD with 2T
- No USB device connected
- Can locate the external IP address.
- Can access via IE 8.0 / 9.0
- Can login to dyndns

Router limitation
- can only accept 16 entries port forwarding

[jokemeister]

To be clear you say you cant ping the DS on your LAN. Have you enabled the firewall on the DS? Perhaps it's blocking your ping request. Until you can ping it, you're not going to be able to map the drives.

[finstone]

To be clear you say you cant ping the DS on your LAN. Have you enabled the firewall on the DS? Perhaps it's blocking your ping request. Until you can ping it, you're not going to be able to map the drives.

Thanks a lot.
I can ping and map the drive now.

Cheers,