last resort try gunter's suggestion.. open about:config (edit>configuration>browser configuration..filter by vendor.. change value for k-meleon to firefox value for km version 1.5.2 to 2.0
it's still unlikely to work because this google gear thing relies on so much xul overlays and registered services for firefox.
here's another work around which is more likely ro work.. first install gears for ie. probably already installed because it seems google installs it for both browsers automatically.. just check if gears works in internet explorer..if it does..go to jujuland's extensions page:
http://pagesperso-orange.fr/jujuland46/JujuLand/KMES/KMES-Download.html
download an install IEtab extension or directly from this link:
http://pagesperso-orange.fr/jujuland46/JujuLand/KMES/KMES193_IEtab.zip
after installing ietab extension, download this macro:
http://necb.bizhat.com/kmeleon/ietab.kmm
and save in kmeleon macros folder to replace juju's macro(it's bit outdated and has commands for km 1.1.x and some might not work for km 1.5.
now go to user agen, select custom and enter this value:
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; SPINWAY.COM; .NET CLR 1.1.4322; .NET CLR 2.0.50727)
now when you want to use a link or webpage to open using ie engine , just right click and select open in ietab.. this will make km some sort of an ieshell for that particular website only and enabling gears to work through it just as working in ie.. the advantage is that you can still use kmeleon and won't need to launch a second browser.
test it out with all your google gears sites..hopefully it will work just fine.
for additional support in opening external links(from a bookmark-desktop shortcut etc) directly in ietab, check this post:
http://kmeleonbrowser.org/forum/read.php?1,88552