I found a related Ubuntu question (which I have attached to this bug) where the author suggested moving the card to another slot. I tried this, and the card was detected and plays sound. Hurrah!
However, I know that the original slot is not bad because the card works in Windows. Therefore, there seems to be a problem with Ubuntu being able to find the card on that slot. Although my personal issue has been resolved, I am leaving the bug open because the root cause has not been fixed. I am willing to help diagnose why Ubuntu can't find the card on the original slot. There may be other people who need both slots.
For what it's worth, the slot that does not work is at the bottom of the motherboard.
I found a related Ubuntu question (which I have attached to this bug) where the author suggested moving the card to another slot. I tried this, and the card was detected and plays sound. Hurrah!
However, I know that the original slot is not bad because the card works in Windows. Therefore, there seems to be a problem with Ubuntu being able to find the card on that slot. Although my personal issue has been resolved, I am leaving the bug open because the root cause has not been fixed. I am willing to help diagnose why Ubuntu can't find the card on the original slot. There may be other people who need both slots.
For what it's worth, the slot that does not work is at the bottom of the motherboard.
Working lspci:
00:00.0 Memory controller: nVidia Corporation CK804 Memory Controller (rev a3)
00:01.0 ISA bridge: nVidia Corporation CK804 ISA Bridge (rev a3)
00:01.1 SMBus: nVidia Corporation CK804 SMBus (rev a2)
00:02.0 USB Controller: nVidia Corporation CK804 USB Controller (rev a2)
00:02.1 USB Controller: nVidia Corporation CK804 USB Controller (rev a3)
00:06.0 IDE interface: nVidia Corporation CK804 IDE (rev f2)
00:07.0 RAID bus controller: nVidia Corporation CK804 Serial ATA Controller (rev f3)
00:08.0 RAID bus controller: nVidia Corporation CK804 Serial ATA Controller (rev f3)
00:09.0 PCI bridge: nVidia Corporation CK804 PCI Bridge (rev a2)
00:0a.0 Bridge: nVidia Corporation CK804 Ethernet Controller (rev a3)
00:0c.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:0d.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:0e.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
01:07.0 Multimedia audio controller: Creative Labs SB Audigy (rev 03)
01:07.1 Input device controller: Creative Labs SB Audigy Game Port (rev 03)
01:07.2 FireWire (IEEE 1394): Creative Labs SB Audigy FireWire Port
01:09.0 Mass storage controller: Silicon Image, Inc. SiI 3114 [SATALink/SATARaid] Serial ATA Controller (rev 02)
05:00.0 VGA compatible controller: nVidia Corporation NV45 [GeForce 6800 GTO] (rev a2)
Working lspci -v attached.