Since I installed SW 12.1, Xmoto just wouldn't run properly, start up was incredibly slow and shutting down too. CPU usage from 90 - 100%. Never had any problems with it, but after (clean) installing SW 12.1 I've spent many hours trying to solve this (on both my Slackboxes). First I used the SlackBuild script from Slackbuilds.org, with all kind of versions of Xmoto, then used src2pkg and the binary package from Slacky-eu.
None worked like it should.

Finally I found he solution: downgrade sqlite to sqlite-3.5.7.tar.gz. Thanks to a Debian bugrapport.

Just wanted to share this with you, I guess there are others who struggle with it (I know I did ).

It should be noted that the SlackBuild for Xmoto at slackbuilds.org is for Xmoto 2.4 and NOT the newest 4.2, which is not hosted on SourceForge. The 2.4 version at slackbuilds.org doesn't even list sqlite as a dependency (I haven't tried building it, so I don't know if it's needed or not -- but I would guess not). The newer Xmoto hosted at slacky.eu probably does have an incorrect sqlite dependency -- it should be lower. I don't think it's the fault of slackbuilds.org though, since the newer version is not offered as an option (and doesn't seem to depend on sqlite at all, though I may be incorrect).

what video card do you have and what driver are you using ?

You are right, older versions of Xmoto do not need sqlite.
But the newest versions are more fun.

On both machines I have different Nvidia cards with different Nvidia (3D) drivers. That's not the issue.