Well, since you didn't specify a version for the router, I'll presume version 1.
Have you applied the firmware upgrade available for version 1?
Have you tried a hard reset of the router?
1) hold in the reset button for 30 seconds
2) unplug it while continuing to hold in the reset button
3) after 10 seconds plug the power back in (still continuing to hold the reset button)
4) after another 30 seconds, release the reset button and let the router boot up.
5) Finally do another power cycle on the router without the reset button and when it boots up re-enter your custom settings... e.g. WPA2-AES passphrase, ISP settings (if any), et cetera.
When removing power, you don't need to pull the wallwart from the outlet... you can just unplug the cord from the back of the router, count to 10 and plug it back in.
Since the DW1525 is Atheros-based, you could try
# yum install ath_info
Then you should be able to run
and possibly find out more details about that Dell adapter.
Though the output from
# lspci | grep -i atheros
should give enough info to see if it's on the supported list for the ath5k/ath9k drivers that I believe are installed by default.
Anyway, the DLink unit may well work better with that adapter, since many DLinks use Atheros chipsets. While interoperability has improved greatly since the early days of wireless, there are still some adapters/routers that work better together than with others (and it's not necessarily that they work best only in-brand, either).