This may sound stupid for a simple iwlist but are you running under root? Or issuing a sudo command?
If not - please do so and let me know the results.
Give the list of Access Points and Ad-Hoc cells in range, and
optionally a whole bunch of information about them (ESSID, Qual‐
ity, Frequency, Mode...). The type of information returned
depends on what the card supports.
Triggering scanning is a privileged operation (root only) and
normal users can only read left-over scan results. By default,
the way scanning is done (the scope of the scan) is dependant on
the card and card settings.
This command take optional arguments, however most drivers will
ignore those. The option essid is used to specify a scan on a
specific ESSID. The option last do not trigger a scan and read
left-over scan results.