Apple has pulled a critical security update put out this week because it breaks 64-bit applications.

The update for Mac OS X, issued on Monday, fixed a number of large security holes across the operating system but has also rendered 64-bit optimised applications unusable, causing thousands of companies to field calls from angry customers.

Apple has pulled the update while it finds a workaround.

One company, Wolfram Research, contacted its customers via email to explain why their Mathematica 5.2 stopped working after users installed the Apple update. "Due to an error on the part of Apple, this update prevents any 64-bit-native application from running," said Wolfram in the note to customers. "In particular, this means that Mathematica 5.2 will not run on any G5 system if it has installed this Security Update."

The note went on to say that Apple had stopped distributing the update and informed Wolfram that there is no workaround for the problem.

Wolfram gave customers a script to disable Mathematica's 64-bit capabilities until Apple issues a new security update to rectify the problem - the application works fine in 32-bit mode. In its note to customers, Wolfram indicated that the Apple update would be released "in the very near future".

Apple has refused to comment so far on the situation.

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