Here is the latest output after WINDOWS XP usage for USB non-show and non-mount:

usb 1-1: USB disconnect, address 2
sda : READ CAPACITY failed.
sda : status=0, message=00, host=7, driver=00
sda : sense not available.
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: assuming drive cache: write through
sda : READ CAPACITY failed.
sda : status=0, message=00, host=7, driver=00
sda : sense not available.
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: assuming drive cache: write through
ohci_hcd 0000:00:13.0: auto-wakeup
usb 1-1: new full speed USB device using ohci_hcd
and address 3
usb 1-1: configuration #1 chosen from 1 choice
scsi1 : SCSI emulation for USB Mass Storage devic
es
usb-storage: device found at 3
usb-storage: waiting for device to settle before
scanning
scsi 1:0:0:0: Direct-Access JetFlash TS1GJF11
0 0.00 PQ: 0 ANSI: 2
SCSI device sda: 2047999 512-byte hdwr sectors (1
049 MB)
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: assuming drive cache: write through
SCSI device sda: 2047999 512-byte hdwr sectors (1 049 MB)
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: assuming drive cache: write through
sda: unknown partition table
sd 1:0:0:0: Attached scsi removable disk sda
usb-storage: device scan complete
knoppix@Knoppix:~$ sudo mount sda
mount: can't find sda in /etc/fstab or /etc/mtab
knoppix@Knoppix:~$ mount sda
mount: can't find sda in /etc/fstab or /etc/mtab
knoppix@Knoppix:~$


so it seems to be to my unknowing eye, the partition table problem as you mentioned.

so from here,
using
knoppix@Knoppix:~$sudo mc

I edited etc/fstab to also include this line

/dev/sda/ media/sda auto rw,users,exec 0 0

and etc/mtab
/dev/sda /media/sda auto rw,nosuid,nodev 0 0

in my persistent knoppix.image and booted from bootfrom=/dev/hda1/home/downdirectory/K*.iso


and then restart knoppix before a changed occurred and I was able to then use the USB flash drive normally.

Because this fail to mount USB doesnt happen every time I use Windows XP, it may be also connected to which service pack is installed in windows XP and also which version of internet expolrer is being used.
For the record, the last machine used before the USB plugging problems started in knoppix5.1.1 were Internet Explorer 7 on Windows XP service pack2