Package manager not working

[sroses]

An Error Has Occurred!
2: file() [<a href='function.file'>function.file</a>]: Unable to access /www/freeweb7.com/s/a/r/sargentrose/htdocs/forum/Packages/installed.list
File: /www/freeweb7.com/s/a/r/sargentrose/htdocs/forum/Sources/Subs-Package.php
Line: 498

what does that mean? i couldn't add modification cause that message promt T.T can anyone help Dx i almost died looking for a forum to post this on T...T its for my project DX PLEASE >< T..T

thanks in advance!