Just had the same problem (or at least similiar problem) when I installed Apache 2 and PHP 4.0.7 (-dev). Did you configure PHP with support for MySQL (of course you did?) - then it might be the problem.
"uncompress" has something to do with zlib, which the MySQL client use and isn't compiled into PHP. You can check if libz.so is linked from libphp4.so using
$ ldd libphp4.so
First line should be
libz.so.1 => /usr/lib/libz.so.1 (0x40144000)
...if everything is ok. If not, read this for a solution and explanation. Maybe.
http://www.faqts.com/knowledge_base/view.phtml/aid/5087