WIF is Base58. Private key with K or L are from compressed address and you'd end up with different address if you convert it.
You sure you didn't get the wrong private key?
Not sure, but I haven't seen others having problems with something like that. I thought they were different, since blockchain.info lets you pick Base58 or WIF.
Well, it seems like you're right. I checked my blockchain.info wallet which have some imported addresses and the private keys doesn't have checksum which is really odd.
You can convert it by using casascius' bitcoin address utility (
wiki,
download link), follow these steps:
1. Open 'Address > Enter an address/key' and enter blockchain.info's WIF key.
2. Copy the hex private key of the address that was added (view its details by right clicking it).
3. Open 'Tools > Base58 calculator' and enter the copied hex.
4. Go to 'Mode > Use Checksum' and make sure that it's checked and copy the base58 result.
5. Same as step 1 but enter the result from 4 instead.
6. Now your real address should be added. Just view the details and copy the WIF private key and import it to electrum.
Might want to wait few hours before doing this to let other users view this post. I'm pretty sure it's safe but just in case.