Embarrassing retreat imminent!

I am trying to install Knoppix on my wife's Compaq 5020 desktop (c.199. Everything has gone well EXCEPT there seems to be a problem with Linux accessing the serial port.

We are using an external serial modem, which has worked fine in the past on both Windows and Linux. The same version of Knoppix is running with no problems as a hard disk install on my generic box so there doesn't seem to be a bug in the distro.

dmesg shows this from boot:
PCI: Found IRQ 11 for device 00:14.2
usb-uhci.c: USB UHCI at I/O 0x2000, IRQ 11
usb-uhci.c: Detected 2 ports
usb.c: new USB bus registered, assigned bus number 1
hub.c: USB hub found
hub.c: 2 ports detected
usb-uhci.c: v1.275:USB Universal Host Controller Interface driver
Serial driver version 5.05c (2001-07-0 with MANY_PORTS SHARE_IRQ SERIAL_PCI ISAPNP enabled
Linux agpgart interface v0.99 (c) Jeff Hartmann
agpgart: Maximum main memory to use for agp memory: 123M
agpgart: Detected Intel 440LX chipset
agpgart: AGP aperture is 64M @ 0x50000000
ttyS0: LSR safety check engaged!
ttyS0: LSR safety check engaged!
ttyS1: LSR safety check engaged!
ttyS1: LSR safety check engaged!
blk: queue c0334960, I/O limit 4095Mb (mask 0xffffffff)
parport0: PC-style at 0x378 [PCSPP,TRISTATE,EPP]
parport0: Printer, Hewlett-Packard HP LaserJet 5L
lp0: using parport0 (polling).
lp0: console ready
ttyS0: LSR safety check engaged!
ttyS1: LSR safety check engaged!
<dmesg output ends at this point>

I have spent some time looking at "LSR safety check engaged!" on the web but so far the only useful thing I can find suggests possible conflicts with PnP, and as you can see 'ISAPNP' (presumably a module) is enabled, but I'm afraid my ignorance extends to not having any ideas what to do next!

For the record setserial returns the following:
setserial -a /dev/ttyS0
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
Baud_base: 115200, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal skip_test

setserial -a /dev/ttyS1
/dev/ttyS1, Line 1, UART: 16550A, Port: 0x02f8, IRQ: 3
Baud_base: 115200, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal skip_test

When the modem is queried on /dev/modem, ttyS0, ttyS1,... the result is always "Unable to detect modem"

The BIOS supplied by Compaq for this model and era has almost no facilities for adjusting settings---nothing at all re PnP, so I don't think I can do anything via that path.

My wife is actually willing to give Linux a go, but internet access is vital for her post-grad studies, so if anyone has any useful advice onmaking progress with this it would be really welcome.


Regards, alamla