More details on the maps you used, did you use entity, or h2g and h2core? There is an 80 MB map size limit for multiplayer maps, so if it's more than that you need to edit the map type in the map header to single player and it'll allow bigger maps.
If you did the conversion using H2C/H2G then it will automatically switch map sizes for you. If you did it on your own, you have to change the map type yourself.
Remembering the good times...
[Ace Mods] [Mod Sqwad]