This relates to #5586 but is worthy of it's own ticket.
From DD32 on wp-testers:
PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature
Unfortunately, Its something which i dont know how to work around, It appears to be > that the Zip class in use doesnt work 100% under certain web hosters setups..
I tracked it down to a small section of code, some Binary maths, Which makes no
sense to me, All i could tell, was that there was a chance that the integer was
reaching its maximum size or something (in other words) not much).
I'm using PHP 5.0.5 on the host affected by my bug.
From further investigation with DD32 it seems that some of the code in pclzip assumes that it is working with 32bit numbers.
This ticket is for us to work on resolving these issues.