The ACPI tables of the Acer Aspire 1691WLMi and several other Aspire and Travelmate models contain a few bugs. If you are interested in (and have trouble) running Linux on one of these machines, you might be interested in the fixed DSDTs.
One of the more nasty bugs is, that the MADT (Multiple APIC Description Table) claims the presence of two IO-APICs, although only one is actually present.
The Linux kernel presently panics when noticing this condition, which will usually leave you without any indication of the real problem, as the console has generally not been initialized at this stage.
To work around this, you can either boot with the option noapic, or apply one of the patches below before compiling your own kernel.