I find they frequently get stuck open if you have a near-full-screen application open.
Is it possible to disable them?
Open "regedit" as adminstrator.
Navigate to:
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced]
Find "ShowInfoTip", right-click and select "Modify" and change the value to "0"
You might be experiencing this issue, described on Microsoft's Q/A forum:
Why does the tooltip display on taskbar icons when I am not hovering my cursor on them?
The suggestion there is to make sure your video drivers are up to date. For a momentary fix, you can try:
dwm.exe
.Click Start>Run, type Gpedit.msc. Under User Configuration>Administrative Templates>Start Menu and Taskbar, enable 'Remove Balloon Tips on Start Menu items'