I use eshop with WordPress 2.7, when I update to WordPress 2.8, the eshop does not work well, and after search eshop forum, many people got the same question, and the author of eshop warning people if update to WordPress 2.8, would met many issues, many plug-ins will not work well under WordPress 2.8

iText 2.1.6 Released on June 16, 2009, and announced the support timestamps and ocsp (timestamp support inspired by contributions by Aiken Sam and Martin Brunecky). also introduced many other changes,

• PdfPKCS7: Added the RIPEMD algorithm.
• AcroFields: Some tools produce invisible signatures without an entry in the page annotation array.
• SpecialSymbol: If PHI is ‘F’ the phi should be ‘f’.
• Removed some unnecessary e.printStackTrace occurences.

and so on, for details, please visit here.