For all machines, use to check that gzip was compiled correctly.
Try compiling gzip without any optimization if you have a problem. Executables for various systems are available here: 99.9% of the problems with gzip are due to file transfers done in ASCII mode instead of BINARY mode.
If you just say "gzip doesn't work" I cannot provide any help.
The gzip sources, written in C, are available here in various formats: on MSDOS or other systems, see the FAQ of the comp.compression newsgroup.
Its main advantages over compress are much better compression and freedom from patented algorithms.
It has been adopted by the GNU project and is now relatively popular on the Internet.
To compile This is the same problem as above: a transfer not made in binary mode has corrupted the gzip header, thus fooling gunzip into emitting an incorrect error message. Please note that gzip, 7-zip, Power Archiver 6.1 and Win-GZ are freeware but you must register Winzip and Power Archiver You know this already, but let me repeat it again: there is no substitute for backups.
If you have a question about gzip, look first for an answer in this page. Please give as much information as possible, at least the name of your operating system (Windows XP, Linux...), the exact command that you typed and the exact error messages that you get.
gzip 1.2.4 may crash when an input file name is too long (over 1020 characters).
The buffer overflow may be exploited if gzip is run by a server such as an ftp server. The beta version 1.3.3 already includes a sufficient patch; use this version if you have to handle files larger than 2 GB.
To test a file, do: If you transfer the file to another machine, test the destination file (after the file transfer), not the source file. If you are not using tar, do at least to test important files.
Once the damage is made, it is somewhere between extremely difficult and impossible to recover damaged files.
Decompression with zcat outputs the correct data plus an error message length error that you can ignore for a single file.