always errors when installing -

Hi.

First of all, great Module.
Second, all the new or update plugins I install work perfectly!!

BUT..... I always get the following errors, when installing new modules or updating exsisting modules:
warning: ftp_chdir() [function.ftp-chdir]: Invalid number of arguments ................/sites/all/modules/plugin_manager/ftp.backend.inc on line 142
warning: ftp_chdir() [function.ftp-chdir]: Invalid number of arguments ................/sites/all/modules/plugin_manager/ftp.backend.inc on line 145

The last one (line 145) is repeated a number of times (number depends on installed plugin).

Anyone, any idea what this could be?

grtz,
Twan