Google's GMarkerManager makes maps not to show

When the "Google's GMarkerManager" option is on - maps do not appear and Firefox gives the following error details:

Drupal.gmap.marker has no properties
[Break on this error] Drupal.gmap.marker.add = function(marker) {
gmarkermanager_ma... (line 12)
a.q() has no properties
[Break on this error] function S(a,b){var c=this;c.a=a;c.md=a.m();c.yc=a.q().getProjection();b=b||{};c...
maps2.69.api.js (line 1055)

This is from IE

Line: 1056
Char: 45
Error: 'q()' is null or not an object

Everything works fine when "No marker" is chosen... I haven't tried the "Jef Poskanzer's Clusterer" option yet.