I find it weird though that I hit this limit now. I´ve been running SAB 0.4.11 for 6 months on a Windows 2008 machine without this problem. For me this only happened after upgrading to 0.5.0 Beta5 and Beta6.shypike wrote: It's a rather hairy subject, because every OS/filesystem has it own limits.
Most OS-es don't even report back the cause properly.
My temporary download folder was D:\SABnzbd_downloads\incomplete, but when using a Newzbin Usenet (Raw) search and creating an NZB for non-indexed content, the resulting download path became D:\SABnzbd_downloads\incomplete\selected_files_20100113-013202\xxxxxxxx_xxxxx_xxxxxx.part001.rar.
Changing to D:\temp didn´t help as D:\temp\selected_files_20100113-013202\xxxxxxxx_xxxxx_xxxxxx.part001.rar was still too long.
Solution was to also rename the default named NZB (selected_files_20100113-013202.nzb) created by Newzbin to something shorter. A cumbersome workaround for what is otherwise a fantastic program.