I haven't fooled with this in awhile, but think when I last tried this, I was in an edit session and executed this on a selection...dividing the selection into equal intervals from the specified start (or end) point.
I have used the split line tool when in an edit session. However 1, it only allows you to split the line up into a maximum of 999 parts. 2, the distance option is wired, because when you entre 100 or entre 1000 or entre and figure say 627 the line gets split into 2 parts wired.
A more involved solution if this fits your situation and you don't mind the extra work is to use Linear Referencing tools. Basically what you'd need to do is create a route from the desired line features and specify the end you want to start 'measuring' from. Then you could create points along the route at the designated interval....I think you'll need an input table, easy enough to create. ....those 2 tools are in the Linear Referencing toolbox, I think Create Routes and Make Route Event.... (I'm relying on memory here.)
Once you have the the points, it's an easy matter of splitting the line at the point intersections...there's a separate tool for that.
That should give you more precisely what you ask, hope that helps.
I have found the answer. Download and install the ET Geo Wizards add-in for ArcGIS desktop. Then use the Split Polyline Wizard in this toolbox. You can break up the line what ever way you want. As in by length, percentage etc. The Geo Wizard tool box should be in everyone's tool box set as it has often saved my. Lately ArcGIS has a bunch of tools that don't work and I have found the Geo Wizard to fill in the short comings of ArcGIS.