Troubleshooting fonts can be one of the most frustrating endeavors, since many times small changes can result in small and unexpected behaviors, including application interfaces not loading, but more commonly garbled text. Many times applications will install their own fonts in the global or user library, which in itself may be enough to cause a conflict with existing fonts.
Recently, MacFixIt reader "Carrick" contacted us with a small fix to a problem with Flash forms, where text was being displayed as little black dots. When browser-related issues like this happen, many times the first steps are to troubleshoot the browser. This includes removing all but the Flash plug-in, reinstalling Flash, clearing temporary items in the user account that may affect Flash, and trying different version of Flash (upgrading or downgrading). In this process items like fonts are often overlooked.
Carrick found that this problem appears to happen when fonts that Flash needs are not available. This could happen if the fonts (especially system fonts) are either disabled, or are otherwise not accessible by the system (permissions problems come to mind). In this case, using Suitcase Fusion to re-enable the Helvetica and Helvetica Neue fonts was the solution.
If you have a similar issue, try the following steps:
Run general maintenance.
Boot into Safe Mode and run a permissions fix on the boot drive with Disk Utility, followed by a reputable cleaning program such as Maintenance (or its big brother OnyX), Snow Leopard Cache Cleaner, or Yasu. In particular, use these programs to clear the system and user font caches, then reboot the system normally.
Using Font Book, select all your fonts and choose "Validate Fonts" from the File menu. Disable or uninstall any fonts that have errors, especially if you do not use them. Check any fonts with errors against those found in the /System/Library/Fonts/ folder to see if those are the ones with problems. In particular, those in the following list:
Check for and remove duplicate fonts.
The system may have multiple instances of the same font, or fonts with the same name. You can use Font Book's "Resolve Duplicates" feature for any duplicate fonts, but it also may help to browse through them manually. Fonts can be found in the following directories:
If you find duplicates in or among any of these directories, first remove those found in the user library (/username/Library/Fonts/), followed by those found in the global library (/Macintosh HD/Library/Fonts/). Do not remove any fonts found in the System library, as these are required for proper system function (items like the log-in window, the Finder, and other important system applications.
Use a third-party font utility
In this case, Carrick was able to re-enable the Helvetica and Helvetica Neue fonts using Suitcase Fusion. This is a robust and popular font management application, but others that may be of use include FontExplorer X (and the "Pro" version) and FontAgent Pro.