This article covers bugs and limitations of the widely used application Photoshop and hopefully their workarounds. Some problems are system specific (different flavours of Mac OS and Windows), some are found in a certain program version (like Photoshop Elements, 7.x, 8.x aka CS or 9.x aka CS2) or file type specific (e.g. 16 bit TIFF files with alpha masks). Some of the workarounds might advise to use a different application for a certain task.
Opening large TIFFs with Photoshop
Photoshop CS for Windows has a bug when opening TIFF files that exceed a certain size and are compressed using the packbit format. If you try you get the error message "Could not open ... because of a program error". When this error occurs, it is possible to open the images if they are compressed using a different algorithm. Adobe developer Chris Cox is said to have claimed that a Microsoft compiler bug in the CS version is the reason for this error. It should be partly solved in CS2.
Defining the exact size of a file that produces this kind of error is difficult. According to Erik Krause the bug has something to do with a wrong type cast from 16 to 32 bit integer, watch out for layer size, channel size, pixel size...
Changing the compression can be done with any program that can open the file and save it back (caution! some image viewers - IrfanView f.e. - silently degrade 16 bit TIFFs to 8 bit). A more convenient choice is to use ImageMagick together with Erik Krauses batch file  for TIFF conversion.
There might be problems using LZW compression due to patent issues - although the patent should have expired in all countries by now (see  for details). If this is the case, try no compression or ZIP compression. Newer versions of ImageMagick are not limited anymore.
Resizing introduces a visible seam line
Up to Photoshop CS 2 this is a common problem on both platforms. It only happens when a file is not reduced to the background layer (or flattend) prior to resizing. Before flattening make sure you have saved a copy of your layers file (normally a PSD or PSB) when you think you might need those layers again. To restore your photos you can use mac photo recovery tool.