70 seconds for just the "Searching for GRML file, this may take a few seconds...".

After 70 seconds I get "  -> Mounted live system on /dev/sr0"

Lots of error messages in dmesg.  The particular messages between about the 4th
and 64th seconds in the log were a series of 6 lines repeated about every 6 or 7
seconds consisting of (only readable text copied):

Unhandled sense code
Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Sense key : Hardware Error [current]
Add. Sense: Time out on logical unit
end_request: I/O error, dev sr0, sector 490552
Buffer I/O error on device sr0, logical block 61319

There were other different error message throughout the dmesg output before and
after the ones above that didn't seem to cause a noticeable delay.

Can I send you a copy of the dmesg output?

I'll try a USB CD-ROM and see if there is a difference.

Thanks,
Fletcher