@Vistaboy : Please do what @looking4awayout did (and it's the thing I always recommend when troubleshooting): create a new pristine FxESR 45.x.x profile, devoid of any extensions; safe mode only disables extensions and some gfx related features (e.g. HW acceleration, if applicable), but doesn't negate the existing prefs.js file inside your dirty profile!
You didn't tell us how your existing profile was initially created; often times, profile corruption due to mysterious extension interactions/conflicts, extension upgrades/downgrades and profile migration from different browser versions (from a higher Fx version to a lower one, not to mention between Firefox forks) may be the source of difficult to dissect issues...
BTW, can you still bookmark a URL via other approaches, e.g. the "star" toolbar button?
Best regards