We are seeing more cases of this lately.

There is a known issue with some new video drivers on Windows XP. This affects both 32 and 64 bit systems. It seems that after installing the new drivers, the system is unable to use or install Postscript OpenType fonts. When attempting to install Postscript OpenType fonts, you might receive the message: "Unable to install the [fontname] (OpenType) font. The font file may be damaged. Check with your font vendor about obtaining a new file." Additionally, double-clicking on one of the installed fonts returns the error: "The requested file [path with fontname] is not a valid font file." PS OpenType fonts also do not show up in any programs. The issue is not isolated to Letterhead Fonts only, but all PS OpenType fonts. This affects both Nvidia and ATI drivers.

The following fix has worked in most cases. The fix involves modifying your System Registry. Please make sure you know what you are doing before attempting to change your Registry. A mistake can seriously damage the system. If you are not comfortable changing the Registry, have someone who is perform the tweak for you. Letterhead Fonts cannot be held responsible for any damages this may cause your system. That said, here is the fix that works in most cases. It should not do any harm if it does not work.

•  Click Start button, then choose Run

•  Type:  regedit

•  Click OK button

•  Navigate to:
HKEY_LOCAL_MACHINE / SYSTEM / CurrentControlSet / Control / Session Manager / Memory Management

•  Click on the Memory Management folder

•  Go to Edit > New > DWORD Value

•  Name the value: SessionImageSize

•  Right click on SessionImageSize and choose Modify

•  For Base, choose Decimal and type 20 for the Value Data. Then click the OK button

•  Close the Registry Editor and restart the computer

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If the fix does not work, you might try uninstalling the current video driver. Then, before installing an older version of the driver, run a driver cleaner to completely remove all traces of the faulty driver. Here are two that we know of:

Driver Sweeper  (free)
Driver Cleaner  (not free)

After removing the driver, install an older version of it.

If you have discovered another fix for this issue, please let us know so we can pass that along to other users.

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Links around the internet concerning this issue:

http://snowulf.com/archives/553-OpenType-Font-not-installing.html

http://www.thomasphinney.com/2008/12/no-font-instal/

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*** UPDATE MARCH 12, 2010 ***

Nearly a year later we are still hearing reports of this issue from customers installing the latest drivers. The latest case involved a customer using an Nvida Geforce 9800 GT card. After using Driver Sweeper to remove the new faulty driver, he installed an old driver from the original CD. However, this still did not work. He had to download an even older driver from Nvida's website. The driver that finally worked for his 9800 GT card was: 191.07. He reports that after the driver was installed, Windows did it's own update.