You say the log shows that LPT1 is disabled. I am not sure where you see that in the log. When I search for lpt in the log, there is only one entry.
Above that is the config for the port, showing that it has happily accepted 0x378 hex as 888 dec.
As I showed in my original post, I have issued the vboxmanage commands you suggested.
The vbox file very clearly shows that lpt1 is enabled=true.
Are you saying that the LPT1 is case sensitive? Is that the only thing I missed?
I don't see how reissuing the same commands I have reissued multiple times already will resolve the issue, personally.
You say that interrupt support for the guest needs to be disabled. That flies completely in the face of the documentation, which clearly states that the values used when issuing the "vBoxManage modifyvm <vmname> --lpt1" are for what is visible in the guest. If the interrupt is not supported, then, what value goes in for the IRQ. Leaving the IRQ blank results in an error.
--lpt<1-N> <I/O base> <IRQ> Specifies the I/O address of the parallel port and the IRQ number that the Parallel Port feature will be using. Use this after --lptmod. I/O base address and IRQ are the values that guest sees i.e. the values avalable under guest Device Manager.
So, are you suggesting I disable interrupt on the Host, or Guest?