Does not display axis label in graph when exported to excel

I have a wierd issue.I have a report with graph with coloum chart and axis labels description on x axis.WHen i export the report to PDF everything looks OK.But when i export it to excel few axis labels disapper.Out of 12 labels only 2 apper when exported to excel.Has anyone encountered this issue.

If so is there a way to fix this.

PS: I am using BO XI 3.1 Webi.

Thank you,

Sanjeev