weird characters when typing!

Im not sure if this is a known problem.

Im running version 2.48.1 on windows xp and each session of using blender, after a while the normal character set changes to a set of ‘foreign’ letters


I called the file ‘rotating blades’ and this came out = ÑÏÔÁÔÉÍÃ ÂËÁÄÅÓ.blend!

this applies to anyhwere I type (object names etc)

Any ideas?