Try this, clear your logs
Connect to the NAS with the wired system then try with the wireless and compare the log.
Also ping your wireless systems in "tools" "system check".
Portforwarding may be an option.
NAT Endpoint Filtering
The NAT Endpoint Filtering options control how the router's NAT manages incoming connection requests to ports that are already being used.
Endpoint Independent
Once a LAN-side application has created a connection through a specific port, the NAT will forward any incoming connection requests with the same port to the LAN-side application regardless of their origin. This is the least restrictive option, giving the best connectivity and allowing some applications (P2P applications in particular) to behave almost as if they are directly connected to the Internet.
Address Restricted
The NAT forwards incoming connection requests to a LAN-side host only when they come from the same IP address with which a connection was established. This allows the remote application to send data back through a port different from the one used when the outgoing session was created.
Port And Address Restricted
The NAT does not forward any incoming connection requests with the same port address as an already establish connection.
Note that some of these options can interact with other port restrictions. Endpoint Independent Filtering takes priority over inbound filters or schedules, so it is possible for an incoming session request related to an outgoing session to enter through a port in spite of an active inbound filter on that port. However, packets will be rejected as expected when sent to blocked ports (whether blocked by schedule or by inbound filter) for which there are no active sessions. Port and Address Restricted Filtering ensures that inbound filters and schedules work precisely, but prevents some level of connectivity, and therefore might require the use of port triggers, virtual servers, or port forwarding to open the ports needed by the application. Address Restricted Filtering gives a compromise position, which avoids problems when communicating with certain other types of NAT router (symmetric NATs in particular) but leaves inbound filters and scheduled access working as expected.
Just curious you didn't mention what firmware your running.
DIR-655 Firmware Release Notes
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Firmware: 1.32NA
Date: 07/20/09
1. Fix when disable DHCP server and enable DHCP server, LAN PC cannot get IP.
2. Fix using wireless client to configure Access Control rules, cause DUT reboot.
3. Fix UPnP bug.
4. Disable CAPTCHA by default
5. Fixed QRS issue, can't set up wireless setting.
6. Fixed Router DHCP IP range issue.
7. Fixed WPS UI Show Error warning message.
8. Fix potential security leak with CAPTCHA.
9. Fix USB LED issue about Shareport.
10.Fix Shareport HP932C with Wins 7 issue
11. Fix if set more than 8 Trigger or Firewall port in Application Rules. It will show Warning message.
12. Fix bug: When QRS set wan type of rt to DHCP, the rt will not set Primary and second DNS.
Note: This firmware does not allow downgrading to pre-1.3x.
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Firmware: 1.31NA
Date: 04/28/09
1. New SharePort support PC/Mac (Requires New Utility Installed on PC or Mac to work)
2. Add SecureSpot 2.0
3. CAPTCHA (Cryptographic Authentication)
4. Fix DHCP server issue.
5. Modify the turn from "Network USB" to "SharePort" in the option of "My USB Type is:"
6. Add Advanced DNS Service feature.
7. Remove 3G feature (not a supported feature by North America ISP).
8. Fix LLTD wrong icon in Vista.
9. Fix reboot issue when connecting to Internet
10. Fix if set more than 8 Trigger or Firewall port in Application Rules, it will show warning message.
11. Fix bug: When QRS set wan type of rt to DHCP, the rt will not set Primary and second DNS.
12. This firmware can not be downgraded to previous versions.
13. Guest Zone disable SharePort support (USB spec v1.05)
14. Router time is not reset when factory reset.
15. Fix schedule end time error.
Note: This firmware does not allow downgrading to pre-1.3x. Please save your configuration file before the upgrade. After the upgrade, please reset to factory default, then upload the configuration file image.
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