I have now changed installed a four-port USB PCI card and it is working very well. Disabled the USB controller on the motherboard - so there either is a hardware issue with the MCP78s chipset that causes USB port problems, or there is something with Linux causing the problem. lspci: 00:00.0 RAM memory: nVidia Corporation MCP78S [GeForce 8200] Memory Controller (rev a2) 00:01.0 ISA bridge: nVidia Corporation MCP78S [GeForce 8200] LPC Bridge (rev a2) 00:01.1 SMBus: nVidia Corporation MCP78S [GeForce 8200] SMBus (rev a1) 00:01.2 RAM memory: nVidia Corporation MCP78S [GeForce 8200] Memory Controller (rev a1) 00:01.3 Co-processor: nVidia Corporation MCP78S [GeForce 8200] Co-Processor (rev a2) 00:01.4 RAM memory: nVidia Corporation MCP78S [GeForce 8200] Memory Controller (rev a1) 00:06.0 IDE interface: nVidia Corporation MCP78S [GeForce 8200] IDE (rev a1) 00:07.0 Audio device: nVidia Corporation MCP72XE/MCP72P/MCP78U/MCP78S High Definition Audio (rev a1) 00:08.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Bridge (rev a1) 00:09.0 SATA controller: nVidia Corporation MCP78S [GeForce 8200] AHCI Controller (rev a2) 00:0b.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Express Bridge (rev a1) 00:10.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Express Bridge (rev a1) 00:12.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Express Bridge (rev a1) 00:13.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Bridge (rev a1) 00:14.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Bridge (rev a1) 00:18.0 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] HyperTransport Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Miscellaneous Control 00:18.4 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Link Control 01:04.0 Multimedia video controller: Internext Compression Inc iTVC16 (CX23416) MPEG-2 Encoder (rev 01) 01:05.0 Multimedia video controller: Conexant Systems, Inc. CX23418 Single-Chip MPEG-2 Encoder with Integrated Analog Video/Broadcast Audio Decoder 01:06.0 USB Controller: NEC Corporation USB (rev 43) 01:06.1 USB Controller: NEC Corporation USB (rev 43) 01:06.2 USB Controller: NEC Corporation USB 2.0 (rev 04) 02:00.0 VGA compatible controller: nVidia Corporation C77 [GeForce 8200] (rev a2) 06:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02 cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 0: 23 0 0 3 IO-APIC-edge timer 1: 0 0 0 1033 IO-APIC-edge i8042 7: 1 0 0 0 IO-APIC-edge 8: 0 0 0 1 IO-APIC-edge rtc0 9: 0 0 0 0 IO-APIC-fasteoi acpi 12: 0 0 5 10935 IO-APIC-edge i8042 14: 0 0 3 4919 IO-APIC-edge pata_amd 15: 0 0 0 0 IO-APIC-edge pata_amd 16: 0 0 0 358 IO-APIC-fasteoi cx18-0 17: 0 0 5 1903 IO-APIC-fasteoi ohci_hcd:usb3 18: 0 0 0 0 IO-APIC-fasteoi ohci_hcd:usb2 19: 0 0 0 162 IO-APIC-fasteoi ehci_hcd:usb1, ivtv0 21: 0 0 0 2237 IO-APIC-fasteoi HDA Intel 22: 0 0 1 385 IO-APIC-fasteoi nvidia 28: 0 0 10 18133 PCI-MSI-edge ahci 29: 0 0 4 8067 PCI-MSI-edge eth0 NMI: 0 0 0 0 Non-maskable interrupts LOC: 26153 26642 21696 32013 Local timer interrupts SPU: 0 0 0 0 Spurious interrupts CNT: 0 0 0 0 Performance counter interrupts PND: 0 0 0 0 Performance pending work RES: 36407 23527 29418 23916 Rescheduling interrupts CAL: 8089 8069 7243 6268 Function call interrupts TLB: 709 670 499 455 TLB shootdowns TRM: 0 0 0 0 Thermal event interrupts THR: 0 0 0 0 Threshold APIC interrupts MCE: 0 0 0 0 Machine check exceptions MCP: 2 2 2 2 Machine check polls ERR: 1 MIS: 0 nvidia is no longer sharing an IRQ with the USB controller and instead, ivtv0 is sharing it. the PVR-150 (which is the ivtv0 device) is working well without any problems while continuing to use the Bluetooth-attached device to the USB along with the USB printer attached.