Quote from: BitcoinArsenal on May 11, 2018, 12:44:24 PM

I wanted to send a transaction. I also have one pending transaction which was not confirmed yet although I rebroadcasted and promoted twice.
I got this message:

Quote

ERROR: PRIVATE KEY REUSE DETECTED!

You are attempting to sign a transaction with input that have an already been used. IOTA uses Winternitz one-time signature (W-OTS) scheme, due to it's `one-time` nature, the security of funds in an address decreases rapidly if you re-sign new transactions using the same key. Please wait for previous transaction to confirm, e.g. by promoting/reattaching, before sending another transaction.

Does it mean I can not send another transaction when an other one is pending?

Try to confirm the pending outgoing transaction. Reattach, promote, wait 15 mins, and repeat. You can use this tool if you don't want to do it via wallet: http://pro.iota.fm/.
Next time better use https://field.carriota.com:443 as node, it will perform these things automatically for you.