So tonight another one of my friends (who lives in the same town as me) bought Worms Reloaded after me harping on about it since release. However sometimes when we try to have a match he gets an error saying "version conflict".

Now, I must have played a million different people both online and from real life by this point and I've never had that happen. The only thing I can think of is that out of all my friends he is the only one who never pre-ordered the game and thus got the pre-order content. Could this be the source of the problem or does anyone know what might be?

Make sure your games are up-to-date.

And both try to verify the in-game cache.
How to:
-Go to the Steam library
-Right-click your game
-Go to: Local Files
-Verify the in-game cache

Well we can both verify fine but still have the problem. Guess we'll be waiting for some patch.

Go to:
C:\Program Files\Steam\steamapps\common\worms reloaded

There is a TXT-file there with a name starting with XOM. See if you can find any errors in that file.

Hmm I've got two of those files but the contents of both of them look like errors and gibberish to me haha.

Hehe, try to find the most recent file. Open it, press CTRL+F and search for the word 'error'.

This might be a solution.

Well the only errors my friend has are these but they are clearly to do with the display and I have the same ones and have been playing so far without a problem:

2636 | WGL_ARB_multisample error initialising extension.
2637 | GL_ARB_multisample error initialising extension.
2641 | GL_NV_pixel_data_range error initialising extension.

The only other things in there that might be relevant are:

43157 | WiFiGame::Update_Wait_Snaps() : snap crcs don't match
43158 | WiFiGame::Update_Wait_Snaps() : random states don't match
43158 | WiFiGame::Update_Wait_Snaps() : peers are *NOT* in synch

But again, I have the exact same thing in my files and I imagine every other player does too.