I'm having the same problem as posted on a few sites, one of which is below.
Is there any workaround, or plan to resolve this in the current version? Any
help appreciated.

http://www.tech-archive.net/Archive/.../msg00281.html

In my scenario, I'm building a Gantt chart style Promotional Calendar
organized by brand and then promotion name. The calendar can often have more
than 100 data points in larger markets. I've built a Gantt chart off of a
pivot table, with some VBA code to mimic functionality you'd get from slicers
in excel 2010 to let people filter the chart. It's pretty lame that the
chart just drops labels when you get over 100 data points, and not something
I can easily convey to an end user.

Thanks.
Ivano