There are 3 DNN installations and one EventReg4.5 (5 star rated)Module:

1 - Dnn 4.9.3 local installation uses sqlExpress2008: EventReg works excellent, without any smallest claim.

2 - Dnn 4.9.0  on WH4Life server uses sqlExpress2005: EventReg works excellent too.

3 - Dnn 4.9.3 on PowerDNN server uses sqlExpress2008: EventReg doesn't work here. By entering data the error max pool size reached crashes the whole application.

PowerDNN is the most modern hosting provider and offers the maximum database conection and the people there can't find any problems. 

We (me and module developer) were tryig to fix this problem for about 3 weeks.

I have almost gave up using this module, but it is so... gut, so ...perfect, givig it up isn't easy because it fullfits all our needs.

As a LAST hope I thought maybe the experts here could have any ideas that may help to solve the problem... 

Thanks for any hint!

Have you communicated with r2i about this? I'm not familiar with the module.

Actually why just on PowerDNN's server? The module works, I also tried it on webhostforasp.net's server. I just thought maybe someone could have a small guess or assumption that may help me further, especially because I know PowerDNN through this site and it seems some people are using it here. Otherwise this problem is so uniqe that no one has known a solution for it so far. i2Int has also considered this problem.

If r2i can't solve the problem, I'm pretty sure that I can't either!

Good luck.

Thanks Joe, I had the luck at last (after 3 hard weeks of living in catch-22 situation). The hint came from Germany.
Here the solution, for those may get sometime the same problem:
PowerDNN installs the lastest version of DNN once you order the server. There was something very unusual (at least for me - I hadn't ever seen it eighter in my installations nor in automated installations on different webservers) in connectionstring:
<....;pooling=true;Connection Lifetime=15;Max Pool Size=15;" ... />

I just removed these 3 properties and everything works perfectly as it should. i2int has an excellent customer support and checked the module and the installtion very often. I just wonder why people there in powerdnn ..., ach, lets forget about it: All's well that ends well.

ah - yes, I had forgotten that one, keep your eye on your web.config file, Plesk tends to add those lines of code randomly - so if one day you find things are not working as they should, check your web.config file first.

Thanks,