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.
As you can see there has been loads of fixes with 1.31 and 1.32. If you not having any problems with 1.21 then why update. If it not broken don't fix it.
I updated to 1.32 and have had no issues but it's only been a few days.
If I were you I'd wait a few weeks to see if people report problems befor updating.