Bandwidth issues Either the sender or the receiver does not have a lot of bandwidth, or the bandwidth available is being used by other programs.
Skype call prioritization If you are engaged in a Skype call, Skype will prioritize the voice traffic over the file-transfer traffic so that your conversation is not disrupted. The file-transfer speed will improve when you end your Skype call. If you are running other programs that use your bandwidth (e-mail, Web browser, and so on), these will affect transfer speed as well.
Files being transferred through a relay host Skype limits file-transfer speed to 5 Kbps during relayed transfers. See Appendix A for more information on relay hosts.