Thread was being aborted exception in user control

I have an .ascx user control for creating dynamic charts from a datatable, which uses an external .aspx page for rendering the chart as a .png image. The control is not functioning as expected (ie. the chart image is not being saved in the specified folder), with the containing page catching a "Thread was being aborted" exception. The containing page itself is rendered correctly, and there is no further use of Response.Redirect or Server.Transfer after the page is loaded. Could the exception arise from the statement within the code behind file of the control where the control's image source is set:
imgGDI.imageURL = "somepage.apsx"
or is the only source likely to be the previous Server.Transfer call to the containing page? I have read other threads regarding the 'Thread was being aborted' exception and Try...Catch blocks, but the solutions detailed do not seem to have any effect.
Any suggestions most welcome.The Thread being aborted exception is the natural generation of a Server.Transfer or Response.Redirect. However a Reponse.Redirect has an option to supress the exception. Response.Redirect("foo.aspx", false);
We're using Server.Transfer("foo.aspx", false). The problem seems to be intermittant at the moment though, which is why I thought the problem may be to do with the external .aspx pages being used for the image source.