Thanks for the report. Do you mean the graph "Visits per visit duration" ? For me it works well in firefox. Can you reproduce on demo ? which URL ?

Yes, I mean the graph that shows how long visits last. Please see the attachment for a screenshot of the widget.

I am using 1.8.2 on my website, waavsolutions.com

Attachment: The widget that is affected by the issue.
MWSnap 2012-08-03, 12_51_19 - Piwik widget.png

Can you reproduce the problem on http://demo.piwik.org/ ?

Yes I can reproduce the problem on demo.piwik.org (see attached files for screen captures in FF 12.0) in both FF 12.0 and Opera 11.64.

To reproduce:

• open demo.piwik.org in a maximized browser window
• go to the bottom left widget ("Dure des visites" or "Length of visits")
• change the graph type from "tag cloud" to "piechart"
• un-maximize the browser windo => all widgets are resized but the pie chart disappears from the webpage while all other widgets retain their previous appearance.

To make the graph appear again, you need to click the pie chart icon.

Attachment: Before resizing
MWSnap 2012-08-03, 16_17_43 - demo.piwik.org - widget before resizing.png

Attachment: After resizing
MWSnap 2012-08-03, 16_17_59 - demo.piwik.org - widget after resizing.png

Attachment: Error log in Firebug's console
MWSnap 2012-08-09, 13_59_23-Piwik-pie chart errors in Firebug.png

I have just added a screenshot of the errors logged in the Firebug console. Maybe that it'll help pinpointing the root cause of this ungodly vanishment

(In [6705]) Fixes #3295, make sure Piwik JQPlot class doesn't transform pie chart data twice.