In Lazarus 2.2.0 a new structure of the XML files (*.lpi, *.lps, *.lpk) was introduced. It replaces the numbered XML nodes used in older versions by unnumbered nodes.
While Lazarus 2.2.0 can read both types of file formats and can also convert between them, older versions cannot read the new structure correctly leading to a lot of difficult-to-understand errors when trying to compile.
fixlp is a small utility program, it converts the new Lazarus XML file format to the format used by older versions.
fixlp <filename1> [, <filename2> [, ...]]
<filenames> are the names of the Lazarus .lpi, .lps or .lpk files (with absolute or relative path) to be converted. Wildcards are allowed.
Source code (in Pascal): SourceForge page.