rangebooster N wireless adapter causing problems

[teddyn]

These are the specs of my desktop computer:
Hiper 580W PSU
Asus A8N-SLi Deluxe Mobo
A64 3800+ (single core)
1 Gb PC 3200 (2x 512)
8800 GTX
X-Fi Xtreme Music
400 Gb WD Hard Drive
Windows XP Home

We recently bought a new Wireless ADSL Router (a D-Link DSL-2740B) to replace our old wireless router. Because of this, I bought a new wireless desktop adapter (so that it would be compliant with the 'N' standard-- the D-Link Rangebooster N 650 Desktop Adapter). I placed it into the PCI slot on my computer and installed the drivers from the CD.

I have had several different problems caused by this adapter. First of all, when the device actually connects up to the internet, my connection is really slow and the signal is practically non-existant, even though the router is in the room next door. Web pages load very slowly (much more slowly than with the previous adapter). For some reason, however, when the adapter is actually working, the X-Fi stops functioning (isn't detected at all) and I have no sound-- I don't even have the volume icon appear on the taskbar. Other times, the wireless icon just remains forever on 'searching for network' and I can't access any web pages.

Has anyone heard of a similar problem before? I can't be the only one having this trouble...

[teddyn]

I should also add that there are two other computers, Dell laptops, which are also connected wirelessly to the same router, but which haven't had any problems at all.

[teddyn]

bump!
Please :'( I'd really appreciate some help!