Seems like you have moved into a "bad" area of the phase diagram, with giant micelles or similar. Here are a few "quick & dirty" suggestions to try and get out of it: dilute with deionized water, dilute with ethanol, add salt (but this might make things worse)....

Hi Cornelia,

               Gelling in case of CTAB wate solution might have occured due to formation of 

 worm like micelles network. You may try to add salt as Mr. Parker suggested or add organic solvent or another surfactant which can cause formation of small spherical micelles due to change in interfacial curvature between water and oil interface.

Another thing you might like to do is using centrifuge machine to separate your product from microemulsion...

Maybe yes, diluting with water and adding SDS or other anionic surfactant. The surfactant complex formed will dissolve in the organic phase (maybe necessary to add some more of it). The particles hopefully will stay dispersed in aqueous phase.

Wouldn't a simple change of temperature be enough to escape from a "bad" area of phase diagram? 

Thank you very much for your suggestions.

I have tried heating it up, but after a while it starts to "gel" again - I think some of the solvent might be evaporating and changing the balance.

I have also tried adding water, maybe I should add more - I will try this next. Or, as suggested, use another solvent.

So thank you for the ideas, I really appreciate it.

As said, there is a way to drastically shift CTAB properties by complexing with anionic surfactant, which than transfers CTAB to the oil, which than should separate, i.e. microemulsion converted to an unstable emulsion.

I agree with Titus, it is need to destroy wormlike micelles that are formed by CTAB at high concentration and in the presence of hydrophilic organic anions like salicilate and electrolytes (addition water or SDS).