The e-mail icons image is on the TNG server in the folder
'C:\Program Files\Datatex\tng\images'.
Image names: "dtx_tng_email_pasiv.gif" and "dtx_tng_email_ms_over.gif".
Note that after 10 minutes the e-mail icon will not be available,
The TNG time out is fixed at 15 minutes.
Try the following:
Browser:
Clear the cookies and history.
Close and open the browser.
Log into TNG(new session).
Check if the browser show error messages,
for example IE will display it in the bottom left-hand corner of the page.